Voltage safety margin and dynamic reactive power reserve assessment method, device, equipment and medium

Abstract

The invention discloses a voltage safety margin and dynamic reactive power reserve evaluation method and device, equipment and a medium, and relates to the field of reactive power voltage control of a power system, and the method comprises the steps: carrying out the clustering of fault scenes through employing historical fault data, and obtaining a plurality of fault scene clusters; establishing a transient voltage safety evaluation model for each fault scene cluster, and evaluating the safety margin of each fault scene cluster by using a safety domain boundary function obtained based on the transient voltage safety evaluation model; establishing a power recovery mechanism dynamic model taking the load equivalent resistance as a state variable; and on the basis of meeting the safety margin, the system reactive power reserve and the minimum reactive power reserve, calling a power recovery mechanism dynamic model and introducing a cotangent value of a power factor to evaluate the voltage support capability of a corresponding fault so as to evaluate the voltage safety margin and the dynamic reactive power reserve. The evaluation efficiency can be improved.

Description

Technical Field

[0001] This invention relates to the field of reactive power and voltage control in power systems, and particularly to a method, apparatus, equipment, and medium for evaluating voltage safety margin and dynamic reactive power reserve. Background Technology

[0002] Currently, a large number of power electronic devices are connected to the power grid. The system contains static reactive power devices such as OLTC (On-Load Tap Changer) and flash capacitor reactors, as well as different types of dynamic reactive power devices such as generators, SVC (Static Var Compensator) and SVG (Static Var Generator). All of these factors make it necessary to accurately account for complex transient processes and consider numerous operating scenarios when assessing the dynamic reactive power reserve of the receiving-end power grid. Therefore, it is necessary to establish a dynamic reactive power reserve assessment model that balances solution accuracy and solution speed, and to achieve rapid solution.

[0003] However, the existing power grid is large in scale, has many control devices, and many anticipated faults, making the calculation of safety margin slow; there are many types of reactive power equipment (static: capacitive reactors / OLTC; dynamic: synchronous condensers / generators / SVC / SVG), with different response characteristics, making it impossible to determine the reactive power reserve capacity, which is not conducive to the smooth progress of the evaluation process; in addition, the short-term / medium-term voltage instability mechanism of large-scale systems is complex, and the corresponding model is also relatively complex, resulting in low efficiency.

[0004] In summary, how to improve assessment efficiency while ensuring the completion of voltage safety margin and dynamic reactive power reserve assessment is an urgent problem to be solved. Summary of the Invention

[0005] In view of this, the purpose of this invention is to provide a method, apparatus, device, and medium for evaluating voltage safety margin and dynamic reactive power reserve, which can improve evaluation efficiency while ensuring the completion of voltage safety margin and dynamic reactive power reserve evaluation. The specific solution is as follows:

[0006] In a first aspect, this application discloses a method for evaluating voltage safety margin and dynamic reactive power reserve, including:

[0007] Historical fault data of the UHV near-area power grid is collected, and the fault scenarios are clustered using the historical fault data to obtain several fault scenario clusters;

[0008] A transient voltage safety assessment model is established for each fault scenario cluster. Based on the transient voltage safety assessment model, the safety domain boundary function is obtained, and the safety margin of each fault scenario cluster is evaluated using the safety domain boundary function.

[0009] Determine the system reactive power reserve and calculate the minimum reactive power reserve based on the system reactive power reserve; the system reactive power reserve is the sum of the maximum effective dynamic reactive power reserves of all generators in the power system;

[0010] The response and control effect of each dynamic reactive power source to transient overvoltage, as well as the time-varying and spatial characteristics of transient voltage instability, are analyzed in order to establish a dynamic model of the power recovery mechanism with the equivalent resistance of the load as the state variable.

[0011] Based on meeting safety margin, system reactive power reserve, and minimum reactive power reserve, the dynamic model of the power recovery mechanism is invoked and the cotangent value of the power factor is introduced to evaluate the voltage support capability of the corresponding fault, so as to assess the voltage safety margin and dynamic reactive power reserve.

[0012] Optionally, the step of clustering fault scenarios using historical fault data to obtain several fault scenario clusters includes:

[0013] The fault scenarios are clustered using the shapelet clustering method and historical fault data to obtain several fault scenario clusters.

[0014] Optionally, the transient voltage safety assessment model is as follows:

[0015] ;

[0016] The security domain boundary function is:

[0017] ;

[0018] in, Represents the injected power vector; Represents the hyperbolic tangent function; and These are the model coefficients; This is the original output of the residual network output layer; The function is represented as a pair Normalization yields The function; and These represent the probabilities of a safe and unsafe prediction result, respectively.

[0019] Optionally, the step of evaluating the safety margin of each fault scenario cluster using the safety domain boundary function includes:

[0020] The current operating point of the power system is determined based on the security domain boundary function, and the critical point calculation model is obtained based on the current operating point and adjustment variables.

[0021] The variables are optimized and adjusted based on the objective function and critical point calculation model to determine the critical point when the function value of the objective function is minimized. The distance between the critical point and the current running point is used as the safety margin of the fault scenario cluster to evaluate the safety margin of each fault scenario cluster.

[0022] The critical point calculation model is as follows:

[0023] ;

[0024] The objective function is:

[0025] ;

[0026] in, Indicates the current running point; Indicates the critical point; Indicates the moderating variable; Indicates the safety margin at the critical point; This represents the loss function.

[0027] Optionally, determining the system reactive power reserve and calculating the minimum reactive power reserve based on the system reactive power reserve includes:

[0028] The sensitivity of reactive power source control after each dynamic reactive power source is connected to the bus under various fault conditions is analyzed based on the sensitivity analysis formula, and a self-response voltage control method based on the threshold of reactive power action issued by self-response is set.

[0029] Based on the sensitivity of reactive power source control and the self-response voltage control method that supports the threshold of reactive power action based on self-response, the reactive power reserve of the system is determined, and the minimum reactive power reserve is calculated based on the reactive power reserve of the system.

[0030] The sensitivity analysis formula is as follows:

[0031] and ;

[0032] in, This represents the change in active power. This represents the change in reactive power; This indicates the change in voltage amplitude; This indicates the change in phase angle; This represents the voltage-reactive power sensitivity coefficient; This indicates the sensitivity of reactive power to voltage amplitude; This indicates the sensitivity of reactive power to phase angle; This indicates the sensitivity of active power to voltage amplitude; This indicates the sensitivity of active power to phase angle;

[0033] Among them, the self-response voltage control method based on the self-response reactive action threshold includes:

[0034] When the voltage at the converter's grid connection point is greater than the threshold for reactive power generation by the self-response mechanism, the voltage deviation is positive, and the converter absorbs reactive power through its self-response mechanism. When the voltage at the converter's grid connection point is less than the threshold for reactive power generation by the self-response mechanism, the voltage deviation is negative, and the converter generates reactive power through its self-response mechanism. When the voltage at the converter's grid connection point is within the safe voltage range, the voltage deviation and the threshold for reactive power generation by the self-response mechanism are both zero, and the absorption or generation of reactive power is prohibited.

[0035] Optionally, the calculation of minimum reactive power reserve based on system reactive power reserve includes:

[0036] If the system dynamic reactive power reserve meets the preset reserve capacity, the maximum load without failure is obtained by increasing the load. The system dynamic reactive power reserve corresponding to the maximum load is taken as the first reactive power reserve, and the system dynamic reactive power reserve at the lowest voltage of the converter bus corresponding to the minimum voltage margin of the converter bus voltage is taken as the second reactive power reserve.

[0037] The minimum value between the first reactive power reserve and the second reactive power reserve shall be taken as the minimum reactive power reserve;

[0038] If the system's dynamic reactive power reserve does not meet the preset reserve capacity, the minimum reactive power reserve is calculated by quadratic curve fitting.

[0039] Optionally, based on satisfying the safety margin, system reactive power reserve, and minimum reactive power reserve of the fault scenario cluster, the step of calling the dynamic model of the power recovery mechanism and introducing the cotangent value of the power factor to evaluate the voltage support capability of the corresponding fault, in order to evaluate the voltage safety margin and dynamic reactive power reserve, includes:

[0040] Based on the mechanism analysis obtained from the dynamic model of the power recovery mechanism, a first voltage support capability assessment model is obtained, and a second voltage support capability assessment model is obtained by introducing the cotangent value of the power factor.

[0041] Based on meeting the safety margin, system reactive power reserve and minimum reactive power reserve, the second voltage support capability assessment model is invoked to assess the voltage support capability of the corresponding fault, so as to evaluate the voltage safety margin and dynamic reactive power reserve.

[0042] The dynamic model of the power recovery mechanism, with the equivalent resistance of the load as the state variable, is as follows:

[0043] ;

[0044] The first voltage support capability assessment model is as follows: ;

[0045] The second voltage support capability assessment model is as follows:

[0046] ;

[0047] in, Indicates non-zero power deviation; Indicates the equivalent resistance of the load; Represents the time constant of resistance change; This indicates the preset target for the active power of the load; Indicates the absorbed active power; This represents the absorbed reactive power; This indicates the preset value of the load equivalent resistance; It represents the derivative of the rate of change of the equivalent resistance of the load with respect to time; Indicates the rate of change of the equivalent resistance of the load; This represents the rate of change of the equivalent resistance of the load; This represents the rate of change of active power absorbed by the load; This represents the cotangent value of the power factor.

[0048] Secondly, this application discloses a voltage safety margin and dynamic reactive power reserve assessment device, comprising:

[0049] The fault scenario clustering module is used to collect historical fault data of the UHV near-area power grid and use the historical fault data to cluster fault scenarios to obtain several fault scenario clusters.

[0050] The safety margin calculation module is used to establish a transient voltage safety assessment model for each fault scenario cluster, obtain the safety domain boundary function based on the transient voltage safety assessment model, and use the safety domain boundary function to assess the safety margin of each fault scenario cluster.

[0051] The reactive power reserve determination module is used to determine the system reactive power reserve and calculate the minimum reactive power reserve based on the system reactive power reserve; the system reactive power reserve is the sum of the maximum effective dynamic reactive power reserves of all generators in the power system;

[0052] The dynamic model building module for power recovery mechanism is used to analyze the response and control effect of each dynamic reactive power source to transient overvoltage and the time-varying and spatial characteristics of transient voltage instability, so as to establish a dynamic model of power recovery mechanism with the equivalent resistance of load as the state variable.

[0053] The evaluation module is used to assess the voltage support capability of corresponding faults by calling the dynamic model of the power recovery mechanism and introducing the cotangent value of the power factor, based on the requirements of safety margin, system reactive power reserve and minimum reactive power reserve, so as to evaluate voltage safety margin and dynamic reactive power reserve.

[0054] Thirdly, this application discloses an electronic device, including:

[0055] Memory, used to store computer programs;

[0056] A processor is used to execute the computer program to implement the aforementioned disclosed method for evaluating voltage safety margin and dynamic reactive power reserve.

[0057] Fourthly, this application discloses a computer-readable storage medium for storing a computer program; wherein, when the computer program is executed by a processor, it implements the aforementioned voltage safety margin and dynamic reactive power reserve assessment method.

[0058] As can be seen, this application collects historical fault data of the UHV near-area power grid, clusters fault scenarios using the historical fault data to obtain several fault scenario clusters; establishes a transient voltage safety assessment model for each fault scenario cluster, obtains the safety domain boundary function based on the transient voltage safety assessment model, and uses the safety domain boundary function to assess the safety margin of each fault scenario cluster; determines the system reactive power reserve, and calculates the minimum reactive power reserve based on the system reactive power reserve; the system reactive power reserve is the sum of the maximum effective dynamic reactive power reserves of all generators in the power system; analyzes the response and control effect of each dynamic reactive power source to transient overvoltage and the time-varying and spatial characteristics of transient voltage instability to establish a dynamic model of the power recovery mechanism with the equivalent resistance of the load as the state variable; on the basis of satisfying the safety margin, system reactive power reserve, and minimum reactive power reserve, calls the dynamic model of the power recovery mechanism and introduces the cotangent value of the power factor to assess the voltage support capability of the corresponding fault, so as to evaluate the voltage safety margin and dynamic reactive power reserve. Therefore, this application establishes a transient voltage safety assessment model for each fault scenario cluster, rather than for each fault, which improves the efficiency of safety margin calculation. This application calculates the minimum reactive power reserve based on the system's reactive power reserve, eliminating the need to set reactive power reserves for every typical operating mode, thus reducing the difficulty of setting the minimum reactive power reserve. Furthermore, setting the minimum reactive power reserve based on the sum of the maximum effective dynamic reactive power reserves of all generators in the power system ensures that the minimum reactive power reserve can support the overall assessment process, preventing situations where reactive power is still needed after the minimum reactive power reserve is depleted. This application establishes a dynamic model of the power recovery mechanism with the equivalent resistance of the load as the state variable, simplifying the model and improving subsequent assessment efficiency. In summary, this application improves assessment efficiency while ensuring the completion of voltage safety margin and dynamic reactive power reserve assessments. Attached Figure Description

[0059] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on the provided drawings without creative effort.

[0060] Figure 1 This is a flowchart of a voltage safety margin and dynamic reactive power reserve assessment method disclosed in this application;

[0061] Figure 2 This is a schematic diagram of the Shapelet clustering learning process disclosed in this application;

[0062] Figure 3 This is a schematic diagram of a single-pole connection between a first-end rectifier station and a constant DC voltage station disclosed in this application;

[0063] Figure 4 This is a schematic diagram of a six-pulse inverter disclosed in this application.

[0064] Figure 5 This is a schematic diagram of a transient equivalent circuit for a commutation failure in a DC transmission system disclosed in this application;

[0065] Figure 6 This application discloses an equivalent circuit diagram for a commutation failure fault.

[0066] Figure 7 This is a schematic diagram of a converter reactive power self-response voltage control disclosed in this application;

[0067] Figure 8 This is a schematic diagram of the reactive power response of a DC near-field unit disclosed in this application;

[0068] Figure 9 This is a schematic diagram of a maximum effective dynamic reactive power reserve disclosed in this application;

[0069] Figure 10 This is a schematic diagram of a typical load modeling of a power system disclosed in this application;

[0070] Figure 11 This is a schematic diagram illustrating the relationship between the active power consumed by a load and its equivalent resistance, as disclosed in this application.

[0071] Figure 12 This is a schematic diagram of the voltage safety margin and dynamic reactive power reserve assessment device disclosed in this application.

[0072] Figure 13 This is a structural diagram of an electronic device disclosed in this application. Detailed Implementation

[0073] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0074] The existing power grid is large in scale, has many control devices, and many anticipated faults, making the calculation of safety margin slow. There are many types of reactive power equipment (static: capacitive reactors / OLTC; dynamic: synchronous condensers / generators / SVC / SVG), with different response characteristics, making it impossible to determine the reactive power reserve capacity, which is not conducive to the smooth progress of the evaluation process. In addition, the short-term / medium-term voltage instability mechanism of large-scale systems is complex, and the corresponding model is also relatively complex, resulting in low efficiency.

[0075] Therefore, this application proposes a voltage safety margin and dynamic reactive power reserve assessment scheme, which can improve assessment efficiency while ensuring the completion of voltage safety margin and dynamic reactive power reserve assessment.

[0076] This application discloses a method for evaluating voltage safety margin and dynamic reactive power reserve. (See also...) Figure 1 As shown, the method includes:

[0077] Step S11: Collect historical fault data of the UHV near-area power grid, and use the historical fault data to cluster fault scenarios to obtain several fault scenario clusters.

[0078] In this embodiment, historical fault data of the UHV near-area power grid is collected and analyzed. Data mining technology is used to deeply mine the historical fault data to discover potential fault modes and patterns. Through data analysis, the types and locations of possible future faults are predicted.

[0079] In this embodiment, the historical fault data and collection method of the UHV near-area power grid are as follows: 1. Data type, (1) Fault record data, Fault time: Record the date and time of the fault occurrence. Fault location: Record the specific location and line information of the fault occurrence. Fault type: Such as short circuit, open circuit, discharge, de-icing jump, hardware breakage, etc. Fault phenomenon: Describe the specific phenomenon when the fault occurs, such as discharge traces, flashover, broken line, etc. Weather conditions: Record the weather conditions when the fault occurs, including temperature, humidity, wind speed, wind direction, etc. (2) Equipment parameter data, Equipment type: Such as transformer, circuit breaker, disconnector, instrument transformer, etc. Equipment model: The specific equipment model and specifications. Equipment operating status: The operating status of the equipment before and after the fault, including load, temperature, vibration, etc. Equipment maintenance record: The regular maintenance, repair and test records of the equipment. 2. Data collection method, (1) Online monitoring, Use the online monitoring system to collect data before and after the fault in real time, such as current, voltage, temperature, etc. Real-time analysis and early warning of online monitoring data, timely detection of potential fault risks. (2) Data mining: Data mining algorithms are used to mine historical fault data samples to identify the operating patterns and regularities of potential faults. Data analysis is then used to predict the types and locations of potential faults in the power system.

[0080] It should be noted that a large number of potential faults exist in actual power systems. Establishing a corresponding safety assessment model for each anticipated fault would inevitably incur a severe computational burden. Furthermore, when the actual system suffers a fault not within the anticipated fault set, it would be impossible to estimate the safety margin in real time, as the established safety margin estimation model heavily relies on the anticipated fault. Since the boundaries of the transient voltage safety domain differ significantly among different fault types, training a general transient voltage safety assessment model and safety boundary for all possible fault types would result in highly conservative assessments and substantial deviations in safety margin estimations. Training a separate assessment model for each possible fault type is impractical. Therefore, by utilizing response time-series data that reflects fault information, and through clustering learning of time-series data containing fault information, significantly different fault types and operating scenarios are automatically divided into N clusters. Each cluster contains transient cases of fault types with similar response characteristics, which can be considered as a single fault scenario. Then, following the method described in the previous section, a safety assessment model is established for each cluster of fault scenarios, improving model construction efficiency while ensuring the accuracy of the assessment results and safety margin estimations.

[0081] In this embodiment, the step of clustering fault scenarios using historical fault data to obtain several fault scenario clusters includes: clustering fault scenarios using the shapelet clustering method and historical fault data to obtain several fault scenario clusters. It should be noted that real-world power systems often have a large number of potential unknown faults. Establishing a corresponding safety assessment model for each anticipated fault would inevitably incur a severe computational burden. Therefore, shapelet clustering learning is used to automatically classify typical scenarios and faults in complex power grids, thereby eliminating the reliance on actual accident information monitoring for transient voltage safety and stability assessment.

[0082] It should be noted that Shapelet clustering learning has a significant advantage in autonomously exploring and discovering the clustering / dispersion characteristics of different data categories. This advantage can be leveraged to automatically classify typical scenarios and accidents in complex power grids, enabling automatic classification of transient accidents driven by time-series response data. This reduces the dependence of transient voltage safety and stability assessments on accident information, enhancing the adaptability of safety assessment models under complex scenarios / accidents. See also Figure 2 The diagram shown is a flowchart of a Shapelet clustering learning process. In the diagram, Shpk represents the preferred subsequence and Gapbest represents the optimal separation coefficient; the details are not described in detail here.

[0083] It should be noted that by performing shapelet search on the data for each feature (such as node voltage, node active power, node reactive power, etc.) using the shapelet clustering method, and then transforming the initial high-dimensional time series dataset S into a distance dataset D based on the most representative subsequence of each feature (i.e., the shapelet), k-means clustering or hierarchical clustering can effectively distinguish significantly different fault types. Before performing hierarchical clustering, the t-distributed stochastic neighbor embedding (t-SNE) algorithm is used to perform two-dimensional visualization of the distance dataset, providing a reference for the number of clusters in the subsequent hierarchical clustering based on the aggregation characteristics of the specific feature space data. For unknown faults not in the expected fault set, in online applications, unknown faults can also be clustered based on the shapelet transformation obtained above. By comparing the distances of these unknown fault samples with the cluster centers in the hierarchical clustering model, each sample is assigned to the cluster to which the nearest cluster center belongs, providing a basis for selecting a suitable safety assessment model for unknown faults.

[0084] It should be noted that data mining and learning based on post-fault time-series response trajectories, combined with hierarchical clustering based on shapelet transform, can reliably cluster fault scenarios, automatically grouping significantly different accidents into clusters and constructing a safety margin estimation model for each cluster's represented operational scenario. The proposed method automatically classifies datasets that originally lacked accident information into typical scenarios of different categories, giving each safety assessment model a certain physical meaning, thus freeing it from the limitations of anticipated accidents to some extent. Simultaneously, the proposed method avoids the potentially large biases that might arise from safety assessment models that do not consider fault information, reducing the number of assessment models and computational burden. Its reliable classification results will significantly improve the efficiency and accuracy of constructing transient voltage safety assessment models for multi-fault scenarios.

[0085] It should be noted that in the offline training phase, time-series response data after a fault is first collected, and fault scenarios are clustered using shapelet transformation. Then, a boundary function and safety margin estimation model based on active learning is established for each fault scenario. The active learning method achieves efficient model training and rapid approximation of the safety boundary in the case of small samples, and the safety margin can be estimated in real time using the known boundary function. In the online application phase, if a potential fault is detected in the expected fault set, the corresponding safety assessment model for the fault scenario is directly selected for safety assessment and margin estimation. If it is not in the expected fault set, a transformation is performed based on the previously searched shapelet, and the distance between these unknown fault samples and the cluster centers in the hierarchical clustering model is compared. Each sample is assigned to the cluster of the nearest cluster center, and the assessment model corresponding to that cluster is selected for online estimation, providing a basis for selecting a close safety assessment model for unknown faults. The method proposed in this paper can evaluate the safety and safety margin of the transient voltage at the current operating point under various fault scenarios in real time during online application. For unsafe assessment results, preventive control measures should be implemented promptly based on the unsafe margin estimated by the safety boundary function of the corresponding fault scenario.

[0086] Step S12: Establish a transient voltage safety assessment model for each fault scenario cluster, obtain the safety domain boundary function based on the transient voltage safety assessment model, and use the safety domain boundary function to assess the safety margin of each fault scenario cluster.

[0087] In this embodiment, a dynamic safety domain is first established. After a certain injected power vector enters the power system, the boundary function of the dynamic safety domain determines the point where the system can maintain transient stability under a certain fault. The function is then used to judge the safety state of the operating point and estimate the safety margin. Specifically, a computer active learning algorithm is used to improve the applicability of the transient voltage safety assessment model to complex and variable power systems in actual situations, even with a limited training sample set, and to achieve an approximate approximation of the transient voltage safety domain boundary. To estimate the safety margin of the power system, a neural network assessment model and other optimization algorithms are used. By adjusting the current operating point of the power system, the critical point closest to the operating point on the boundary surface can be solved. At this point, the distance between the operating point and the critical point of the power system is the safety margin.

[0088] It should be noted that the process of establishing the transient voltage safety assessment model, setting the safety domain boundary function, and calculating the safety margin is as follows:

[0089] (1) Establishing a dynamic security domain: Establishing a security domain for the power system to analyze and evaluate power system security is not only efficient but also accurate. Constructing a precise dynamic security domain for the power system can visualize the transient security of the power system at every moment and provide accurate preventive decisions through calculation and analysis, thus providing reliable support for the safe and stable operation of the current power system energy network. The dynamic security domain needs to consider three stages: before, during, and after a fault. The system state differential equations corresponding to the three stages are:

[0090] ;

[0091] in, For the state variables of the power system, Indicates the stage before a failure. Indicates the stage of the fault. Indicates the post-fault stage. The duration of the fault. If at a given injected power vector... Under the following conditions, an event occurs in the power system at a certain location for a duration of... After a short-circuit fault, if the system is in transient stability, then under the injected power vector, the system is still safe. All injected powers that satisfy the above conditions are grouped into a set, which is the dynamic safety domain in the injected power space. The definition is as follows:

[0092] ;

[0093] in, For the injected power vector, For system state variables, For the transient stability region under the injected power vector, This is the set of injected power before the fault. Corresponding to the pre-fault stage, Corresponding to the post-fault stage, This refers to the fault type. The boundary of the dynamic security domain is represented as... A safety region is a set of points within the injected power set before an accident, under a known fault condition, where the system can maintain transient stability. Each point in the safety region corresponds to a transient stability region. The safety boundary function is known. This allows us to obtain the operational safety status and safe operating range of the operating point. The subscript d stands for domain, meaning domain, and has no special meaning.

[0094] (2) Efficient approximation process of transient voltage safety domain boundary: Active learning reduces the dependence of the data-driven model on the training sample set by actively selecting the optimal value samples for calibration. Therefore, active learning can improve the generalization of the transient voltage safety assessment model to the actual complex and variable power system when the training set is limited. The basic idea of ​​active learning is to start learning from a small initial calibration sample set to obtain an initial assessment model. A batch of optimal value samples are selected for calibration through a certain sample search strategy, the parameters of the assessment model are updated, and the next round of search and training is carried out. Active learning is a cyclical iterative process. The establishment of the data-driven assessment model based on active learning mainly involves two key steps: assessment model training based on the training sample set and key sample search strategy. Among them, the search for key samples depends on the latest assessment model. The searched key samples are sent to the assessment model for training after calibration. The two steps are carried out alternately. When the number of searched calibration samples reaches the limit or the assessment result of the assessment model on the test sample set remains unchanged, active learning ends.

[0095] Let the set of key samples used in training be... ,in: As input to the model, it represents the current operating point of the power system, i.e., the injected power vector of the node; To assess the actual safety of the power system, the output calibration for classification problems is generally represented using one-hot encoding, where [0, 1] represents insecurity and [1, 0] represents safety. Let the number of residual modules in the residual network-based evaluation model be... The module uses a single-layer fully connected approach. Given the transient voltage safety assessment result for the current operating point obtained based on the evaluation model, the mathematical expression of the transient voltage safety assessment model based on the residual network is:

[0096] ;

[0097] in, The injected power vector for the node. These are parameters in the residual module. This is the original output of the residual network output layer. For the process The output of the function after normalization. Let be the normalization function. , These represent the probabilities of a safe and unsafe prediction outcome, respectively. Through function pairs The result was obtained by normalizing to 0-1. The relative magnitudes of the two values ​​already contain the probability information of the predicted class. Therefore, the safety region boundary function obtained by evaluation learning based on the residual network can be expressed as:

[0098] ;

[0099] From the above safety domain boundary function, the analytical expression for the transient voltage safety boundary can be obtained as follows: The judgment rule for transient voltage safety assessment is as follows: This indicates that the current running point is safe. This indicates that the assessment is unsafe.

[0100] (3) Estimation of transient voltage safety margin: Based on the safety domain boundary function characterized by the neural network evaluation model, the shortest distance between the current power system operating point and the stability boundary characterized by the neural network evaluation model is calculated to obtain the safety margin. This helps the dispatcher understand the current situation and provides guidance for subsequent preventive measures.

[0101] To find the shortest distance from the current operating point of the power system to the safety boundary, the parameters of the neural network evaluation model are first frozen. This is achieved by considering the current operating point of the power system. Adjustments were made to obtain the critical point on the variable cross section. At this time, the operating point of the power system With critical point The distance between them is the safety margin. Solving for the safety margin can be viewed as an optimization problem. Due to the critical point... With running point It corresponds. It can be used The first-order function representation introduces the adjustment variable of the optimization problem. By adjusting variables right Adjustments were made to obtain the adjusted critical point. As shown below: For each critical point corresponding to the current operating point of the power system All of these require adjusting variables. Solve an optimization problem. To obtain the current running point... The objective function for optimization, which is the minimum distance to the boundary of the evaluation model, is as follows: , The norm is represented by the parameter obtained through optimization algorithms (such as stochastic gradient descent) based on the objective function. Optimize the function until the objective function value is minimized to obtain the running point. The corresponding nearest critical point The distance between the two represents the safety margin described by the neural network assessment model. This margin can be used to understand the minimum change required at which the power system operating point will alter the results of the safety assessment model. Furthermore, the obtained safety margin can be used to guide subsequent preventative control measures.

[0102] It should be noted that the dynamic safety domain quantifies the transient safety of the system under the current state in real time and provides corresponding decision support. The constructed safety boundary function can be used to judge the safety status of the operating point and estimate the safety margin. The safety domain is trained by active learning, and the safety domain boundary function learned by the residual network-based evaluation learning can evaluate the safe operating status of the operating point. The safety boundary function is characterized by a neural network evaluation model, and the parameters are optimized by the optimization algorithm based on the objective function. The resulting safety margin will be used to guide subsequent prevention and control.

[0103] Step S13: Determine the system reactive power reserve and calculate the minimum reactive power reserve based on the system reactive power reserve; the system reactive power reserve is the sum of the maximum effective dynamic reactive power reserves of all generators in the power system.

[0104] In this embodiment, in order to calculate the system's reactive power reserve and minimum reactive power reserve, it is necessary to pre-calculate the steady-state voltage control value, transient voltage change rate, and transient voltage change amplitude after each dynamic reactive power source is connected to the bus under each fault. Reactive power-voltage sensitivity analysis is required to obtain the self-response voltage control method, and then the system's reactive power reserve and minimum reactive power reserve are calculated.

[0105] It should be noted that this application may refer to the effective dynamic reactive power reserve of the generator that is at the critical reactive power compensation point and continuously experiences DC commutation failure as the maximum effective dynamic reactive power reserve of the generator, and the sum of the dynamic reactive power reserve capacity of all generators as the system reactive power reserve.

[0106] It should be noted that the minimum reactive power reserve can be calculated in the following two ways: (1) Under the consideration of reserved load reserve, the system load is continuously increased until the DC system does not experience continuous commutation failure. The system dynamic reactive power reserve capacity corresponding to the maximum load at this time is called the minimum reactive power reserve capacity; (2) The system dynamic reactive power reserve at the minimum voltage of the converter bus corresponding to the minimum voltage range when continuous commutation failure occurs is called the minimum reactive power reserve capacity.

[0107] It should be noted that the precise assessment of fast / medium / slow reactive power reserves is proposed and defined as the effective dynamic reactive power reserve to cope with continuous commutation failures. Furthermore, the sum of the maximum effective dynamic reactive power reserves of all generators is defined as the system reactive power reserve, and the minimum reactive power reserve capacity is calculated. This can ensure that the system can cope with the risk of insufficient maximum reactive power reserve.

[0108] In one specific embodiment, the process of calculating the steady-state voltage control value, transient voltage change rate, and transient voltage change amplitude after each dynamic reactive power source is connected to the bus is as follows:

[0109] (1) Steady-state voltage control of UHV transmission systems; UHV multi-terminal DC transmissions use a true bipolar connection method, where the voltages of the two poles can be controlled independently, and the voltage control methods used are the same. Therefore, only one pole needs to be studied for voltage control methods. The research objects in the following text are all unipolar. For details, please refer to Figure 3 The diagram shown illustrates a single-pole connection between a head-end rectifier station and a constant DC voltage station; further details will not be elaborated upon here. For each pole, the objective of steady-state voltage control is to control the DC-side port voltage of the converter at the head-end rectifier station to a set reference value. Therefore, the voltage reference value of the DC voltage station It can be represented as:

[0110] ;

[0111] in, This is the voltage reference value for the DC voltage station. This indicates the set reference value for the DC side port voltage of the converter at the first-end rectifier station. This is due to voltage drop. In a parallel multi-terminal DC transmission system, the converter stations are connected together in parallel, including the first-end rectifier station and the constant DC voltage station. Figure 3 This diagram shows a single-pole connection between the first-end rectifier station and the constant DC voltage station. The network topology shown in the diagram can be regarded as a sub-network in a parallel DC power grid. The first converter station is the first-end rectifier station, the nth converter station is the constant DC voltage station, and the n-2 converter stations between them can be called intermediate converter stations.

[0112] (2) Transient voltage variation; The AC bus of the rectifier station is a key bus connecting the DC transmission system and the AC system of the sending-end power grid. Its transient voltage variation characteristics during a fault are crucial, and its transient voltage variation trend lays the foundation for the overall transient voltage variation trend of the sending-end power grid. First, the principle of DC commutation failure is briefly described, and then the formation mechanism of the transient voltage of the AC bus of the rectifier station first decreasing and then increasing is analyzed. Commutation failure is a common fault of the inverter in the inverter station at the receiving end of the DC transmission. It cannot be controlled at the sending end, but it can have a great impact on the sending-end power grid. There are many causes, such as short circuit of the inverter converter valve, loss of the inverter trigger pulse, and AC system fault on the inverter side, all of which can cause commutation failure. This application briefly describes the principle of commutation failure.

[0113] See Figure 4 The diagram shown is a schematic diagram of a six-pulse inverter. A common six-pulse inverter is a basic building block of an inverter station. It consists of six thyristors, each acting as a converter valve. These are valve arms 1-6. During normal operation of the converter valve, they are turned on sequentially according to the pulse triggering sequence. Ideally, at each moment, two non-in-phase thyristors need to be turned on simultaneously, one from the upper half-bridge and one from the lower half-bridge, forming a current-carrying circuit. The process of current transferring from one branch to another is called commutation. As mentioned above, the DC current h is generated by the valve arms... The conduction is transferred to the valve arm. The process of conduction involves one phase commutation. Figure 4 In this context, n and m represent nodes, , and Represents the current in three phases, , and This represents the three-phase voltage, where N represents the neutral point. Indicates DC side current, DC side inductance (grounding inductance, grounding reactor) Indicates DC power supply (voltage). Indicates inductance.

[0114] As the above analysis shows, when commutation failure occurs, it is equivalent to a short circuit on the DC side of the inverter station. The transient equivalent circuit of the DC system commutation failure is as follows: Figure 5 The diagram shown is a schematic representation of a transient equivalent circuit in a DC transmission system during commutation failure. Figure 5 middle, and Indicates the initial phase. and Indicates the DC side voltage of the rectifier station, and These represent the equivalent resistance and reactance on the fault side, respectively. and These represent the equivalent resistance and reactance on the rectifier side, respectively. Indicates fault current. and Between and and Both are variable capacitors, the one on the left. left and right The diode is located on the right side; during commutation failure, the inverter side of the DC system loses back electromotive force. The electromotive force (EMF) on the secondary side of the rectifier station suddenly drops to 0, and the DC voltage on the rectifier side at the moment of the fault... It will decrease with a short circuit on the inverter side. The voltage drop on the AC busbar caused by the voltage transmitted through the transformer in the rectifier station leads to a decrease in the AC busbar voltage K. At the moment of the fault, the rectifier firing angle α cannot be adjusted instantaneously and has a certain delay. To simplify the calculation, the rectifier before the fault is considered as a voltage source. Its fault equivalent circuit Figure 6 As shown, this is an equivalent circuit diagram of a commutation failure fault.

[0115] Figure 6 middle, , These represent the resistance and inductance on the DC side, respectively. , These represent the resistance and inductance on the commutation side, respectively. These are the coefficients when a three-phase system is equivalent to a single-phase system. Figure 6 The rightmost two are rectifier diodes, the middle one is a capacitor, and the leftmost one is... The lower part is the DC excitation; due to the rectifier station adjusting the initial phase... When the angle exceeds 90°, the rectifier is shut down, and the system sheds the load. ( This indicates the active power of the rectifier station. (This represents the reactive power of the rectifier station.) Before the rectifier is turned off, the rectifier station absorbs a large amount of reactive power, so the DC system can be considered as an inductive load, which has a demagnetizing effect on the generator armature reaction. After the DC load is removed, the demagnetizing effect disappears. However, due to the conservation of magnetic flux, the magnetic flux of the excitation winding cannot change abruptly. Therefore, the generator maintains its original electromotive force at the moment of load removal. After the load is removed, the reactance flowing through the generator is equivalent to the reactance of the line. The current I drops sharply, the voltage drop decreases, and the AC bus voltage of the rectifier station rises rapidly to the system's equivalent power supply potential. Subsequently, due to the rectifier station filter not being disconnected during the commutation failure fault after load shedding, a capacitive load is retained. The capacitive current exerts an armature reaction on the generator, magnetizing it. At this time, the AC bus voltage of the rectifier station becomes:

[0116] ;

[0117] in, This refers to the power frequency transient overvoltage of the AC bus of the rectifier station. This represents the filter capacitive reactance that was not removed from the rectifier station. For the line equivalent reactance, Let be the armature reaction reactance of the generator. From the above equation, it can be seen that... Compared to E, a further increase leads to a transient overvoltage on the AC bus of the rectifier station. After the inverter commutation failure fault ends, the inverter resumes normal operation, and the DC short circuit disappears. At this time, the DC current begins to recover, and the rectifier station reduces 'a' to its steady-state setting value, thus reducing the reactive power consumption of the rectifier station. However, any filters that were not disconnected will feed reactive power back to the system. Therefore, during the DC current recovery period, the rectifier station has a large reactive power surplus, further contributing to the sharp rise in the transient voltage on the AC bus. The greater the DC transmission power before the fault, the greater the reactive power compensation required by the rectifier station, and the larger the capacitance of the filters (the smaller the reactance value), resulting in a higher transient overvoltage on the AC bus caused by the commutation failure. Similarly, the smaller the equivalent impedance of the AC system, the higher the transient overvoltage on the AC bus of the rectifier station.

[0118] In this embodiment, determining the system reactive power reserve and calculating the minimum reactive power reserve based on the system reactive power reserve includes: analyzing the reactive power source control sensitivity after each dynamic reactive power source is connected to the bus under each fault based on the sensitivity analysis formula, and setting a self-response voltage control method based on the reactive power action threshold issued by the self-response; determining the system reactive power reserve based on the reactive power source control sensitivity and the self-response voltage control method supporting the reactive power action threshold issued by the self-response; and calculating the minimum reactive power reserve based on the system reactive power reserve.

[0119] The sensitivity analysis formula is as follows:

[0120] and ;

[0121] in, This represents the change in active power. This represents the change in reactive power; This indicates the change in voltage amplitude; This indicates the change in phase angle; This represents the voltage-reactive power sensitivity coefficient; This indicates the sensitivity of reactive power to voltage amplitude; This indicates the sensitivity of reactive power to phase angle; This indicates the sensitivity of active power to voltage amplitude; This indicates the sensitivity of active power to phase angle;

[0122] The self-response voltage control method based on the self-response reactive power generation threshold includes: when the converter grid connection point voltage is greater than the self-response reactive power generation threshold, the voltage deviation is positive, and the converter absorbs reactive power through self-response; when the converter grid connection point voltage is less than the self-response reactive power generation threshold, the voltage deviation is negative, and the converter generates reactive power through self-response; when the converter grid connection point voltage is within the safe voltage range, the voltage deviation and the self-response reactive power generation threshold are 0, and the absorption or generation of reactive power is prohibited.

[0123] It should be noted that when performing reactive power-voltage sensitivity analysis on a distribution network, since the power matrix of the distribution network is approximately constant during normal operation, if the voltage of a certain node exceeds the threshold, based on the already analyzed reactive power-voltage sensitivity, the converter of the corresponding node can perform reactive power self-response action, thereby establishing the reactive power self-response voltage threshold for transient overvoltage, thus completing the reactive power self-response voltage control of the converter.

[0124] Specifically, the sensitivity analysis process is as follows: When the grid connection point voltage exceeds the limit, the reactive power-voltage sensitivity determines the magnitude of the converter's reactive power self-response action. Therefore, reactive power-voltage sensitivity analysis of the distribution network is required. The relationship between the change in system injected power and the change in system node voltage is as follows:

[0125] ;

[0126] For photovoltaic converters, to maximize photovoltaic absorption, maximum power point tracking (MPPT) is generally used on the photovoltaic side of the converter, and active power reduction is not performed when there is still reactive power regulation capacity. For energy storage converters, the focus of this embodiment is on the relationship between reactive power and voltage, therefore, active power regulation is not performed on the energy storage converter. In summary, we can conclude that:

[0127] ;

[0128] The voltage-reactive power sensitivity coefficient is strongly correlated with the network topology parameters. Under normal operation, it is approximately a constant matrix. If the distribution network structure does not change, it does not need to be updated in real time. Therefore, when a node experiences a voltage over-limit, the converter of the corresponding node performs a reactive power self-response action based on the calculated reactive power-voltage sensitivity to suppress the voltage over-limit.

[0129] Specifically, the reactive power self-response voltage control settings are as follows: Introducing the concept of a reactive power action threshold in reactive power self-response voltage control, the converter grid connection point voltage is compared with this action threshold, and a reactive power self-response voltage control method for the converter is proposed:

[0130] (1) This is the threshold for self-response reactive power absorption. The voltage at the converter's grid connection point at the current moment is taken as... ,when When the voltage at the converter's grid connection point is higher than the self-response reactive power absorption threshold, the voltage deviation is positive, and the converter self-response absorbs reactive power to suppress overvoltage at the grid connection point.

[0131] ;

[0132] (2) The threshold for issuing reactive power actions in a self-response manner. When the voltage at the converter's grid connection point is lower than the threshold for reactive power output by the self-response mechanism, the voltage deviation is negative, and the converter outputs reactive power to support the grid connection point voltage.

[0133] ;

[0134] in for Voltage deviation at the grid connection point of the converter at any time for The actual voltage at the grid connection point of the converter at any given time. The threshold for self-response absorption of reactive power. The threshold for reactive power action is to be issued in a self-response manner. for Reactive power input of the converter at any time. for The reactive power output value of the converter at any given time. This represents the self-response complex power.

[0135] (3) When At this time, the voltage operates within a safe range. To reduce unnecessary reactive power flow and shorten the lifespan of the converter, the voltage deviation and reactive power self-response action value are set to zero.

[0136] ;

[0137] in, for The actual voltage at the grid connection point of the converter at any given time. for Reactive power input of the converter at any time. for The reactive power output value of the converter at any given time.

[0138] See Figure 7 The diagram shown is a schematic of a converter's reactive power self-response voltage control, illustrating the relationship between various threshold values. This is the rated voltage at the converter's grid connection point.

[0139] In this embodiment, the calculation of minimum reactive power reserve based on system reactive power reserve includes: if the system dynamic reactive power reserve meets the preset reserve capacity, then the maximum load without failure is obtained by increasing the load, and the system dynamic reactive power reserve corresponding to the maximum load is taken as the first reactive power reserve, and the system dynamic reactive power reserve at the lowest voltage of the converter bus corresponding to the minimum voltage margin of the converter bus voltage is taken as the second reactive power reserve; the minimum value between the first reactive power reserve and the second reactive power reserve is taken as the minimum reactive power reserve; if the system dynamic reactive power reserve does not meet the preset reserve capacity, then the minimum reactive power reserve is calculated by quadratic curve fitting.

[0140] In this embodiment, a precise assessment of fast / medium / slow reactive power reserves is proposed. The specific assessment method is as follows: The generator excitation control system responds to the drop in generator terminal voltage. The input signal is the difference between the generator terminal voltage and the voltage reference value. The generator excitation voltage is changed through PID (Proportional-Integral-Derivative) control, excitation limiting, and other processes, thereby improving the generator reactive power output. Compared to conventional generators, the new synchronous condenser has a larger excitation multiple and a faster excitation speed, and the subtransient reactance is also significantly reduced, resulting in an instantaneous reactive power output capacity improvement of over 50%. A typical reactive power output curve of a near-field generator during DC commutation failure is shown below. Figure 8 The diagram shown is a schematic representation of the reactive power response of a DC near-field generator unit. Figure 8 As can be seen, after an AC short-circuit fault, the generator terminal voltage drops sharply, and the generator reactive power output increases rapidly, potentially reaching the excitation limit. After the fault is cleared, the voltage recovers, and the reactive power output decreases rapidly. Subsequently, corresponding to a second voltage drop at the converter bus, the generator reactive power output increases again to [a higher level]. .

[0141] Dynamic reactive power reserve of a generator is generally defined as the additional reactive power that a generator can actually generate during a transient process under a certain fault. For continuous commutation failure requirements, the additional reactive power generated by the generator before the AC fault disappears is clearly not the focus. The main factor in suppressing the secondary voltage drop of the converter bus is the additional reactive power generated by the generator after the fault is cleared. Therefore, it is defined as an effective dynamic reactive power reserve to cope with continuous commutation failures. : ;in, To address the issue of effective dynamic reactive power reserve in the event of continuous commutation failures, To reflect the effective coefficient of dynamic reactive power generation of generators, For generator Maximum reactive power output capability For generator Initial reactive power output before the fault.

[0142] The effective dynamic reactive power reserve of the generator, as defined above, varies under different operating conditions. As the DC transmission power increases, more reactive power is required for DC power recovery after a fault, correspondingly requiring the generator to generate more reactive power. Furthermore, as the load power of the DC receiving-end grid increases, this can be equivalent to a reduction in the DC near-area reactive power compensation capacity. The secondary voltage drop at the converter bus is larger, also requiring the generator to provide more reactive power. The reactive power reserve assessment method proposed in this embodiment is primarily for online applications, where the DC transmission power changes little in most cases. Therefore, drawing inspiration from the VQ curve method (Voltage-Reactive Power Curve Method), the effective dynamic reactive power reserve of the generator at the critical point is defined as the maximum effective dynamic reactive power reserve by gradually withdrawing the DC near-area reactive power compensation capacitor (while maintaining a constant DC effective short-circuit ratio) until a continuous DC commutation failure occurs. Figure 9 The diagram shown is a schematic of a maximum effective dynamic reactive power reserve.

[0143] After obtaining the dynamic reactive power reserve capacity of a single generator, the system reactive power reserve is defined as the sum of the maximum effective dynamic reactive power reserves of all generators: Where, in the formula: To address the issue of effective dynamic reactive power reserve in the event of continuous commutation failures, For effective dynamic reactive power summation.

[0144] It should be noted that in actual system operation, after calculating and obtaining the effective dynamic reactive power reserve of the system, it is also necessary to determine the threshold value of the reactive power reserve capacity. When the system reactive power reserve is less than the threshold value, an alarm should be triggered, and corresponding measures should be taken. After obtaining the system reactive power reserve, the minimum reactive power reserve capacity (minimum reactive power reserve) can be calculated based on the system reactive power reserve. Specifically: in addition to meeting the requirement of not causing continuous commutation failures after a fault in the current mode, the system's dynamic reactive power reserve is mainly to provide the required reactive power after possible increases in system load and other power fluctuations. The following two methods are used to evaluate the minimum reactive power reserve capacity:

[0145] (1) By increasing the system load, considering that the DC system will not experience continuous commutation failure under the reserved load margin (e.g., 10%), the dynamic reactive power reserve of the system corresponding to the maximum load is taken as the minimum reactive power reserve capacity.

[0146] (2) The distance between the lowest voltage of the converter bus and the critical commutation voltage during fault recovery represents, to some extent, the risk of continuous commutation failure. This can be mitigated by setting a minimum voltage margin for the converter bus voltage, and using the minimum voltage margin corresponding to the lowest voltage of the converter bus as the minimum reactive power reserve capacity. The DC near-area reactive power compensation capacitors are gradually phased out until continuous commutation failure occurs. The threshold value for the system's reactive power reserve capacity is calculated as follows: However, when the system's dynamic reactive power reserve capacity is insufficient, the above method cannot calculate it. and For the corresponding operating point (where consecutive commutation failures have occurred previously), consider using a quadratic curve fitting method to obtain the minimum reactive power reserve capacity of the system.

[0147] Starting from the current operating mode, disabling the DC near-zone reactive power compensation capacitor can obtain parameters along the predetermined path. Dynamic reactive power reserve of the system under changing direction Select multiple points The curve is used to estimate the minimum reactive power reserve capacity of the system. The curve can be fitted using the following quadratic curve.

[0148] Step S14: Analyze the response and control effect of each dynamic reactive power source to transient overvoltage and the time-varying and spatial characteristics of transient voltage instability in order to establish a dynamic model of the power recovery mechanism with the equivalent resistance of the load as the state variable.

[0149] In this embodiment, when analyzing the response and control effect of various dynamic reactive power sources on transient overvoltage, it is necessary to study the generation and entire process of transient overvoltage under AC / DC faults, analyze the differences in the response control characteristics of various types of dynamic reactive power sources during the entire transient overvoltage process under AC / DC faults, and finally obtain the impact of the differences in the response control characteristics of dynamic reactive power sources on transient overvoltage. It should be noted that modeling the power load and establishing a load dynamic model considering the power recovery mechanism can derive the positive and negative feedback regions between the active power consumed by the load and the equivalent resistance, as well as the transient voltage instability criteria.

[0150] It should be noted that transient overvoltage refers to the voltage rise caused by a rapidly increasing high-voltage pulse superimposed on the supply voltage. It typically occurs after a power system transition process, such as circuit breaker operation or a short-circuit fault, and the system returns to a state of temporary stability. In AC / DC hybrid power grids, DC blocking, commutation failure, and AC faults can all lead to transient overvoltages. The generation and overall process analysis of transient overvoltages are shown below:

[0151] (1) DC blocking fault; When a bipolar blocking occurs in the DC system, the DC equipment stops operating, resulting in almost zero active power transmission and reactive power consumption in the DC system. At this time, all the reactive power generated by the AC filter is input into the AC system, further increasing the AC bus voltage at the sending end, thereby generating overvoltage.

[0152] (2) Commutation failure; Commutation failure will cause the DC current and trigger angle to drop rapidly, the absorption of reactive power will decrease, the AC bus voltage of the rectifier station will recover, but the increase of reactive power will lead to overvoltage.

[0153] (3) AC faults; when a fault such as a three-phase short circuit occurs on the AC side, the commutation voltage will drop, and the DC voltage will also drop accordingly. During the fault recovery period, transient overvoltages may occur due to the transition process of the power system.

[0154] It should be noted that various types of dynamic reactive power sources exhibit differences in their response control characteristics. Under AC / DC faults, multiple types of dynamic reactive power sources will respond and attempt to control transient overvoltages. These dynamic reactive power sources include synchronous condensers, STATCOMs (Static Synchronous Compensators), and SVCs (Static Var Compensators). They differ significantly in response speed, regulation range, and control strategies. The differences in the response control characteristics of various types of dynamic reactive power sources are shown below:

[0155] (1) Synchronous condenser; Response speed: Synchronous condensers have a fast response speed and can provide or absorb a large amount of reactive power in a short time. Adjustment range: Its adjustment range is relatively large, which can meet the reactive power compensation requirements under different voltage levels. Control strategy: A constant voltage control strategy is usually adopted, which maintains the bus voltage stability by adjusting the excitation current.

[0156] (2) STATCOM; Response speed: STATCOM has an extremely fast response speed, capable of adjusting reactive power within milliseconds. Adjustment range: Its adjustment range is also relatively large, and it can continuously and smoothly adjust reactive power. Control strategy: It usually adopts a constant reactive power or constant voltage control strategy, and dynamically adjusts according to system requirements.

[0157] (4) SVC; Response speed: The response speed of SVC is relatively slow, but still within an acceptable range, and can meet the reactive power compensation needs in most cases. Adjustment range: Its adjustment range is limited, but it can be expanded by combining different types of capacitors and reactors. Control strategy: A segmented control strategy is usually adopted, which changes the reactive power output by switching capacitors and reactors.

[0158] It should be noted that the differences in response control characteristics among different types of dynamic reactive power sources have a significant impact on the suppression effect of transient overvoltage. The impact of the differences in the response control characteristics of dynamic reactive power sources on transient overvoltage is shown below:

[0159] (1) Impact of response speed: Dynamic reactive power sources with fast response speed (such as STATCOM) can respond to transient overvoltages more promptly and take measures to suppress them, thereby more effectively reducing the amplitude and duration of overvoltages.

[0160] (2) Impact of adjustment range: Dynamic reactive power sources with a large adjustment range (such as synchronous condensers and STATCOM) can provide reactive power compensation over a wider voltage range, thus responding more flexibly to different voltage fluctuations.

[0161] (3) Impact of control strategies: Different control strategies have different effects on suppressing transient overvoltages. For example, the constant voltage control strategy can maintain the bus voltage stability, but may not be able to completely suppress transient overvoltages; while the constant reactive power control strategy can dynamically adjust the reactive power output as needed, thereby better suppressing transient overvoltages.

[0162] Step S15: Based on meeting the safety margin, system reactive power reserve and minimum reactive power reserve, call the dynamic model of the power recovery mechanism and introduce the cotangent value of the power factor to evaluate the voltage support capability of the corresponding fault, so as to evaluate the voltage safety margin and dynamic reactive power reserve.

[0163] In this embodiment, the step of evaluating the voltage support capability of the corresponding fault by invoking a dynamic model of the power recovery mechanism and introducing the cotangent value of the power factor, based on satisfying the safety margin, system reactive power reserve, and minimum reactive power reserve of the fault scenario cluster, in order to evaluate the voltage safety margin and dynamic reactive power reserve, includes: obtaining a first voltage support capability evaluation model based on the mechanism analysis obtained from the dynamic model of the power recovery mechanism, and obtaining a second voltage support capability evaluation model by introducing the cotangent value of the power factor; and evaluating the voltage support capability of the corresponding fault by invoking the second voltage support capability evaluation model, based on satisfying the safety margin, system reactive power reserve, and minimum reactive power reserve of the fault scenario cluster, in order to evaluate the voltage safety margin and dynamic reactive power reserve.

[0164] The dynamic model of the power recovery mechanism, with the equivalent resistance of the load as the state variable, is as follows:

[0165] ;

[0166] The first voltage support capability assessment model is as follows: ;

[0167] The second voltage support capability assessment model is as follows:

[0168] ;

[0169] in, Indicates non-zero power deviation; Indicates the equivalent resistance of the load; Represents the time constant of resistance change; This indicates the preset target for the active power of the load; Indicates the absorbed active power; This represents the absorbed reactive power; This indicates the preset value of the load equivalent resistance; It represents the derivative of the rate of change of the equivalent resistance of the load with respect to time; Indicates the rate of change of the equivalent resistance of the load; This represents the rate of change of the equivalent resistance of the load; This represents the rate of change of active power absorbed by the load; This represents the cotangent value of the power factor.

[0170] It should be noted that analyzing the time-varying and spatial characteristics of transient voltage instability reveals the difference in the correlation between transient voltage instability and the reactive power source ratio. The specific analysis process is as follows:

[0171] Electrical loads can be modeled as dynamic or static models. The dynamic characteristics of the load are typically modeled, without loss of generality, as a power recovery mechanism after a disturbance; see [reference needed]. Figure 10 The diagram shown is a typical load modeling diagram for a power system; where: and These are the equivalent resistance and reactance of the load, respectively. The time constant of the resistance change , and These are the preset target for the active power of the load, the absorbed active power, and the reactive power, respectively. For load node voltage, Let S be the load current, and S be a complex variable with Laplace variation. The function f represents the dynamic model of the power recovery mechanism. After a disturbance, if the active power absorbed by the dynamic load deviates from the preset target, it will adjust its resistance according to physical laws or control logic in an attempt to reduce the power deviation.

[0172] Specifically, the dynamic model of the power recovery mechanism, described by the equivalent resistance of the load as the state variable, is shown below:

[0173] ;

[0174] If the scenario involves the power source supplying power to the load via a transmission network, it can be equivalent to Thevenin's theory. Figure 10 As shown, the load consumes active power. Its equivalent resistance Relationship such as Figure 11 The diagram shown illustrates the relationship between the active power consumed by a load and its equivalent resistance. This represents the active power of the power transmission network. This represents the reactive power of the power transmission network. Represents the equivalent reactance of the transmission network. Indicates load, The load consumes reactive power. Indicates the power source of the power transmission network. Represents the power transmission network current. This represents the load voltage. It can be determined that the curve to the right of B represents the positive feedback region of the load state operation. If a non-zero power deviation exists in this region... Power recovery mechanism control The change will further amplify the power deviation. Similarly, the curve segment between O and B represents the negative feedback region.

[0175] However, not all positive feedback regions are unstable. If the load state is between B and C, although it is currently in the positive feedback region, the state will eventually move beyond B and stabilize at the equilibrium point A. Therefore, the region between B and C is stable, and only the area to the right of C is unstable. The stable and unstable regions are marked in green and yellow in the diagram, respectively. If a disturbance causes the load state to enter the positive feedback unstable region, its equivalent resistance will continuously decrease, and the power factor will continuously deteriorate, thus increasing reactive power consumption. If the grid's reactive power support capacity remains unchanged, this will lead to voltage collapse at the load node. Voltage stability is a local problem; if it can be determined that the load state at a certain node has entered the positive feedback indeterminate region, it can be determined that transient voltage instability will occur at that node.

[0176] Based on the above analysis, a strategy for assessing the voltage support capability of dynamic / static reactive power control equipment can be proposed. Specifically, based on the mechanism analysis of the power recovery model, when the load is in an unstable region and causes transient voltage instability, a positive feedback process occurs, resulting in a decrease in the equivalent resistance of the load and a reduction in power consumption. Therefore, the following formula can be proposed for assessing the voltage support capability of dynamic / static reactive power control equipment:

[0177] ;

[0178] However, the equivalent resistance of the load is usually difficult to measure, so we consider using responsive electrical quantities to make the above equation measurable. The power factor angle of the load during power restoration satisfies the following equation:

[0179] ;

[0180] in, The cotangent value of the power factor angle of the load. The active power absorbed by the load. The reactive power absorbed by the load. The equivalent resistance of the load is . The equivalent reactance of the load, Equivalent resistance rate of change, Equivalent resistance The rate of change.

[0181] To illustrate the mechanism criterion for transient voltage instability that can be equivalently expressed using the cotangent value of the power factor angle, the following classification discussion is conducted. When , hour, The cotangent of the load power factor angle changes in the same direction as the equivalent resistance; when , hour, The cotangent of the power factor angle changes in the same direction as the equivalent resistance. Similarly, it can be proven that as the equivalent resistance of the load increases, i.e. When the value is greater than 0, the similarity rule is satisfied.

[0182] ;

[0183] This allows for the equivalent derivation of the voltage support capability assessment in the load positive feedback instability region based on the power factor mapping. Both the active and reactive power of the load can be measured at the bus node.

[0184] ;

[0185] Thus, the assessment of the safety and stability margin and dynamic reactive power reserve of UHV AC / DC near-area voltage was completed.

[0186] As can be seen, this application collects historical fault data of the UHV near-area power grid, clusters fault scenarios using the historical fault data to obtain several fault scenario clusters; establishes a transient voltage safety assessment model for each fault scenario cluster, obtains the safety domain boundary function based on the transient voltage safety assessment model, and uses the safety domain boundary function to assess the safety margin of each fault scenario cluster; determines the system reactive power reserve, and calculates the minimum reactive power reserve based on the system reactive power reserve; the system reactive power reserve is the sum of the maximum effective dynamic reactive power reserves of all generators in the power system; analyzes the response and control effect of each dynamic reactive power source to transient overvoltage and the time-varying and spatial characteristics of transient voltage instability to establish a dynamic model of the power recovery mechanism with the equivalent resistance of the load as the state variable; on the basis of satisfying the safety margin, system reactive power reserve, and minimum reactive power reserve, calls the dynamic model of the power recovery mechanism and introduces the cotangent value of the power factor to assess the voltage support capability of the corresponding fault, so as to evaluate the voltage safety margin and dynamic reactive power reserve. Therefore, this application establishes a transient voltage safety assessment model for each fault scenario cluster, rather than for each fault, which improves the efficiency of safety margin calculation. This application calculates the minimum reactive power reserve based on the system's reactive power reserve, eliminating the need to set reactive power reserves for every typical operating mode, thus reducing the difficulty of setting the minimum reactive power reserve. Furthermore, setting the minimum reactive power reserve based on the sum of the maximum effective dynamic reactive power reserves of all generators in the power system ensures that the minimum reactive power reserve can support the overall assessment process, preventing situations where reactive power is still needed after the minimum reactive power reserve is depleted. This application establishes a dynamic model of the power recovery mechanism with the equivalent resistance of the load as the state variable, simplifying the model and improving subsequent assessment efficiency. In summary, this application improves assessment efficiency while ensuring the completion of voltage safety margin and dynamic reactive power reserve assessments.

[0187] Accordingly, embodiments of this application also disclose a voltage safety margin and dynamic reactive power reserve assessment device, see [link to relevant documentation]. Figure 12 As shown, the device includes:

[0188] The fault scenario clustering module 11 is used to collect historical fault data of the UHV near-area power grid and use the historical fault data to cluster fault scenarios to obtain several fault scenario clusters.

[0189] The safety margin calculation module 12 is used to establish a transient voltage safety assessment model for each fault scenario cluster, obtain the safety domain boundary function based on the transient voltage safety assessment model, and use the safety domain boundary function to assess the safety margin of each fault scenario cluster.

[0190] The reactive power reserve determination module 13 is used to determine the system reactive power reserve and calculate the minimum reactive power reserve based on the system reactive power reserve; the system reactive power reserve is the sum of the maximum effective dynamic reactive power reserves of all generators in the power system;

[0191] The dynamic model establishment module 14 for power recovery mechanism is used to analyze the response and control effect of each dynamic reactive power source to transient overvoltage and the time-varying and spatial characteristics of transient voltage instability, so as to establish a dynamic model of power recovery mechanism with load equivalent resistance as state variable.

[0192] The evaluation module 15 is used to evaluate the voltage support capability of the corresponding fault by calling the dynamic model of the power recovery mechanism and introducing the cotangent value of the power factor, based on the requirements of safety margin, system reactive power reserve and minimum reactive power reserve, so as to evaluate the voltage safety margin and dynamic reactive power reserve.

[0193] The more specific working process of each of the above modules can be found in the corresponding content disclosed in the foregoing embodiments, and will not be repeated here.

[0194] As can be seen, this application collects historical fault data of the UHV near-area power grid, clusters fault scenarios using the historical fault data to obtain several fault scenario clusters; establishes a transient voltage safety assessment model for each fault scenario cluster, obtains the safety domain boundary function based on the transient voltage safety assessment model, and uses the safety domain boundary function to assess the safety margin of each fault scenario cluster; determines the system reactive power reserve, and calculates the minimum reactive power reserve based on the system reactive power reserve; the system reactive power reserve is the sum of the maximum effective dynamic reactive power reserves of all generators in the power system; analyzes the response and control effect of each dynamic reactive power source to transient overvoltage and the time-varying and spatial characteristics of transient voltage instability to establish a dynamic model of the power recovery mechanism with the equivalent resistance of the load as the state variable; on the basis of satisfying the safety margin, system reactive power reserve, and minimum reactive power reserve, calls the dynamic model of the power recovery mechanism and introduces the cotangent value of the power factor to assess the voltage support capability of the corresponding fault, so as to evaluate the voltage safety margin and dynamic reactive power reserve. Therefore, this application establishes a transient voltage safety assessment model for each fault scenario cluster, rather than for each fault, which improves the efficiency of safety margin calculation. This application calculates the minimum reactive power reserve based on the system's reactive power reserve, eliminating the need to set reactive power reserves for every typical operating mode, thus reducing the difficulty of setting the minimum reactive power reserve. Furthermore, setting the minimum reactive power reserve based on the sum of the maximum effective dynamic reactive power reserves of all generators in the power system ensures that the minimum reactive power reserve can support the overall assessment process, preventing situations where reactive power is still needed after the minimum reactive power reserve is depleted. This application establishes a dynamic model of the power recovery mechanism with the equivalent resistance of the load as the state variable, simplifying the model and improving subsequent assessment efficiency. In summary, this application improves assessment efficiency while ensuring the completion of voltage safety margin and dynamic reactive power reserve assessments.

[0195] Furthermore, embodiments of this application also provide an electronic device. Figure 13This is a structural diagram of an electronic device 20 according to an exemplary embodiment. The content of the diagram should not be construed as limiting the scope of this application.

[0196] Figure 13 This is a schematic diagram of the structure of an electronic device 20 provided in an embodiment of this application. The electronic device 20 may specifically include: at least one processor 21, at least one memory 22, a display screen 23, an input / output interface 24, a communication interface 25, a power supply 26, and a communication bus 27. The memory 22 stores a computer program, which is loaded and executed by the processor 21 to implement the relevant steps in the voltage safety margin and dynamic reactive power reserve assessment method disclosed in any of the foregoing embodiments. Furthermore, the electronic device 20 in this embodiment may specifically be an electronic computer.

[0197] In this embodiment, the power supply 26 is used to provide operating voltage for each hardware device on the electronic device 20; the communication interface 25 can create a data transmission channel between the electronic device 20 and external devices, and the communication protocol it follows can be any communication protocol applicable to the technical solution of this application, and is not specifically limited here; the input / output interface 24 is used to acquire external input data or output data to the outside world, and its specific interface type can be selected according to specific application needs, and is not specifically limited here.

[0198] Furthermore, the memory 22, as a carrier for resource storage, can be a read-only memory, random access memory, disk, or optical disk, etc. The resources stored thereon may include computer programs 221, and the storage method may be temporary storage or permanent storage. The computer programs 221 may include, in addition to computer programs capable of performing the voltage safety margin and dynamic reactive power reserve assessment method executed by the electronic device 20 as disclosed in any of the foregoing embodiments, computer programs capable of performing other specific tasks.

[0199] Furthermore, embodiments of this application also disclose a computer-readable storage medium for storing a computer program; wherein, when the computer program is executed by a processor, it implements the aforementioned voltage safety margin and dynamic reactive power reserve assessment method.

[0200] The specific steps of this method can be found in the corresponding content disclosed in the foregoing embodiments, and will not be repeated here.

[0201] The various embodiments in this application are described in a progressive manner, with each embodiment focusing on the differences from other embodiments. For the same or similar parts between the various embodiments, refer to each other. As for the apparatus disclosed in the embodiments, since it corresponds to the method disclosed in the embodiments, the description is relatively simple, and relevant parts can be referred to in the method section.

[0202] Those skilled in the art will further recognize that the units and algorithm steps of the various examples described in conjunction with the embodiments disclosed herein can be implemented in electronic hardware, computer software, or a combination of both. To clearly illustrate the interchangeability of hardware and software, the components and steps of the various examples have been generally described in terms of functionality in the foregoing description. Whether these functions are implemented in hardware or software depends on the specific application and design constraints of the technical solution. Those skilled in the art can use different methods to implement the described functions for each specific application, but such implementation should not be considered beyond the scope of this application.

[0203] The steps of the methods or algorithms described in conjunction with the embodiments disclosed herein can be implemented directly by hardware, a software module executed by a processor, or a combination of both. The software module can be located in random access memory (RAM), main memory, read-only memory (ROM), electrically programmable ROM, electrically erasable programmable ROM, registers, hard disk, removable disk, CD-ROM, or any other form of storage medium known in the art.

[0204] Finally, it should be noted that in this document, relational terms such as "first" and "second" are used only to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitations, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes said element.

[0205] The above provides a detailed description of the voltage safety margin and dynamic reactive power reserve assessment method, apparatus, equipment, and storage medium provided in this application. Specific examples have been used to illustrate the principles and implementation methods of this application. The descriptions of the above embodiments are only for the purpose of helping to understand the method and core ideas of this application. At the same time, for those skilled in the art, there will be changes in the specific implementation methods and application scope based on the ideas of this application. Therefore, the content of this specification should not be construed as a limitation of this application.

Claims

1. A method for evaluating voltage safety margin and dynamic reactive power reserve, characterized in that, include: Historical fault data of the UHV near-area power grid is collected, and the fault scenarios are clustered using the historical fault data to obtain several fault scenario clusters; A transient voltage safety assessment model is established for each fault scenario cluster. Based on the transient voltage safety assessment model, the safety domain boundary function is obtained, and the safety margin of each fault scenario cluster is evaluated using the safety domain boundary function. Determine the system reactive power reserve and calculate the minimum reactive power reserve based on the system reactive power reserve; the system reactive power reserve is the sum of the maximum effective dynamic reactive power reserves of all generators in the power system; The response and control effect of each dynamic reactive power source to transient overvoltage, as well as the time-varying and spatial characteristics of transient voltage instability, are analyzed in order to establish a dynamic model of the power recovery mechanism with the equivalent resistance of the load as the state variable. Based on meeting safety margin, system reactive power reserve, and minimum reactive power reserve, the dynamic model of the power recovery mechanism is invoked and the cotangent value of the power factor is introduced to evaluate the voltage support capability of the corresponding fault, so as to assess the voltage safety margin and dynamic reactive power reserve.

2. The method for evaluating voltage safety margin and dynamic reactive power reserve according to claim 1, characterized in that, The method of clustering fault scenarios using historical fault data to obtain several fault scenario clusters includes: The fault scenarios are clustered using the shapelet clustering method and historical fault data to obtain several fault scenario clusters.

3. The voltage safety margin and dynamic reactive power reserve assessment method according to claim 1, characterized in that, The transient voltage safety assessment model is as follows: ； The security domain boundary function is: ； in, Represents the injected power vector; Represents the hyperbolic tangent function; and These are the model coefficients; This is the original output of the residual network output layer; The function is represented as a pair Normalization yields The function; and These represent the probabilities of a safe and unsafe prediction result, respectively.

4. The voltage safety margin and dynamic reactive power reserve assessment method according to claim 3, characterized in that, The method of evaluating the safety margin of each fault scenario cluster using the security domain boundary function includes: The current operating point of the power system is determined based on the security domain boundary function, and the critical point calculation model is obtained based on the current operating point and adjustment variables. The variables are optimized and adjusted based on the objective function and critical point calculation model to determine the critical point when the function value of the objective function is minimized. The distance between the critical point and the current running point is used as the safety margin of the fault scenario cluster to evaluate the safety margin of each fault scenario cluster. The critical point calculation model is as follows: ； The objective function is: ； in, Indicates the current running point; Indicates the critical point; Indicates the moderating variable; Indicates the safety margin at the critical point; Represents the loss function; Represents the norm.

5. The method for evaluating voltage safety margin and dynamic reactive power reserve according to claim 1, characterized in that, The determination of system reactive power reserve and the calculation of minimum reactive power reserve based on system reactive power reserve include: The sensitivity of reactive power source control after each dynamic reactive power source is connected to the bus under various fault conditions is analyzed based on the sensitivity analysis formula, and a self-response voltage control method based on the threshold of reactive power action issued by self-response is set. Based on the sensitivity of reactive power source control and the self-response voltage control method that supports the threshold of reactive power action based on self-response, the reactive power reserve of the system is determined, and the minimum reactive power reserve is calculated based on the reactive power reserve of the system. The sensitivity analysis formula is as follows: and ; in, This represents the change in active power. This represents the change in reactive power; This indicates the change in voltage amplitude; This indicates the change in phase angle; This represents the voltage-reactive power sensitivity coefficient; This indicates the sensitivity of reactive power to voltage amplitude; This indicates the sensitivity of reactive power to phase angle; This indicates the sensitivity of active power to voltage amplitude; This indicates the sensitivity of active power to phase angle; Among them, the self-response voltage control method based on the self-response reactive action threshold includes: When the voltage at the converter's grid connection point is greater than the threshold for reactive power generation by the self-response mechanism, the voltage deviation is positive, and the converter absorbs reactive power through its self-response mechanism. When the voltage at the converter's grid connection point is less than the threshold for reactive power generation by the self-response mechanism, the voltage deviation is negative, and the converter generates reactive power through its self-response mechanism. When the voltage at the converter's grid connection point is within the safe voltage range, the voltage deviation and the threshold for reactive power generation by the self-response mechanism are both zero, and the absorption or generation of reactive power is prohibited.

6. The method for evaluating voltage safety margin and dynamic reactive power reserve according to claim 1, characterized in that, The minimum reactive power reserve calculated based on system reactive power reserve includes: If the system dynamic reactive power reserve meets the preset reserve capacity, the maximum load without failure is obtained by increasing the load. The system dynamic reactive power reserve corresponding to the maximum load is taken as the first reactive power reserve, and the system dynamic reactive power reserve at the lowest voltage of the converter bus corresponding to the minimum voltage margin of the converter bus voltage is taken as the second reactive power reserve. The minimum value between the first reactive power reserve and the second reactive power reserve shall be taken as the minimum reactive power reserve; If the system's dynamic reactive power reserve does not meet the preset reserve capacity, the minimum reactive power reserve is calculated by quadratic curve fitting.

7. The method for evaluating voltage safety margin and dynamic reactive power reserve according to any one of claims 1 to 6, characterized in that, Based on meeting safety margin, system reactive power reserve, and minimum reactive power reserve, the dynamic model of the power recovery mechanism is invoked, and the cotangent value of the power factor is introduced to evaluate the voltage support capability for corresponding faults, in order to assess voltage safety margin and dynamic reactive power reserve, including: Based on the mechanism analysis obtained from the dynamic model of the power recovery mechanism, a first voltage support capability assessment model is obtained, and a second voltage support capability assessment model is obtained by introducing the cotangent value of the power factor. Based on meeting the safety margin, system reactive power reserve and minimum reactive power reserve, the second voltage support capability assessment model is invoked to assess the voltage support capability of the corresponding fault, so as to evaluate the voltage safety margin and dynamic reactive power reserve. The dynamic model of the power recovery mechanism, with the equivalent resistance of the load as the state variable, is as follows: ； The first voltage support capability assessment model is as follows: ; The second voltage support capability assessment model is as follows: ； in, Indicates non-zero power deviation; Indicates the equivalent resistance of the load; This represents the time constant of the resistance change; Indicates the preset target of active power of the load; Indicates the absorbed active power; This represents the absorbed reactive power; This indicates the preset value of the load equivalent resistance; It represents the derivative of the rate of change of the equivalent resistance of the load with respect to time; Indicates the rate of change of the equivalent resistance of the load; This represents the rate of change of the equivalent resistance of the load; This represents the rate of change of active power absorbed by the load; The cotangent value represents the power factor; This represents the rate of change of the cotangent of the power angle; This represents the coupling constraint between the rate of change of active power and the rate of change of reactive power.

8. A voltage safety margin and dynamic reactive power reserve assessment device, characterized in that, include: The fault scenario clustering module is used to collect historical fault data of the UHV near-area power grid and use the historical fault data to cluster fault scenarios to obtain several fault scenario clusters. The safety margin calculation module is used to establish a transient voltage safety assessment model for each fault scenario cluster, obtain the safety domain boundary function based on the transient voltage safety assessment model, and use the safety domain boundary function to assess the safety margin of each fault scenario cluster. The reactive power reserve determination module is used to determine the system reactive power reserve and calculate the minimum reactive power reserve based on the system reactive power reserve; the system reactive power reserve is the sum of the maximum effective dynamic reactive power reserves of all generators in the power system; The dynamic model building module for power recovery mechanism is used to analyze the response and control effect of each dynamic reactive power source to transient overvoltage and the time-varying and spatial characteristics of transient voltage instability, so as to establish a dynamic model of power recovery mechanism with the equivalent resistance of load as the state variable. The evaluation module is used to assess the voltage support capability of corresponding faults by calling the dynamic model of the power recovery mechanism and introducing the cotangent value of the power factor, based on the requirements of safety margin, system reactive power reserve and minimum reactive power reserve, so as to evaluate voltage safety margin and dynamic reactive power reserve.

9. An electronic device, characterized in that, include: Memory, used to store computer programs; A processor for executing the computer program to implement the voltage safety margin and dynamic reactive power reserve assessment method as described in any one of claims 1 to 7.

10. A computer-readable storage medium, characterized in that, Used to store computer programs; wherein, when the computer programs are executed by a processor, they implement the voltage safety margin and dynamic reactive power reserve assessment method as described in any one of claims 1 to 7.

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