A power system small disturbance stability assessment and correction method and system considering the n-1 operating mode
Patent Information
- Authority / Receiving Office
- NL · NL
- Patent Type
- Patents
- Current Assignee / Owner
- GUANGXI UNIV
- Filing Date
- 2025-05-07
- Publication Date
- 2026-06-22
Abstract
Description
A POWER SYSTEM SMALL DISTURBANCE STABILITY ASSESSMENT AND CORRECTION METHOD AND SYSTEM CONSIDERING THE N-1 OPERATING m TECHNICAL FIELD This application relates to the eld of articial intelligence, online assessment, and optimization of static security and stability of power systems, particularly to a power system small disturbance stability assessment and correction method and system considering the N-1 operating mode. BACKGROUND With the rapid and healthy development of the national economy, the electricity demand of various industries has signicantly increased, and power systems are developing towards large-scale, high-capacity, ultra-high voltage, and long-distance transmission. To achieve carbon peak and carbon neutrality, it is necessary to vigorously develop new energy sources dominated by wind and solar energy, promote the construction of a new type of power system with new energy as the main component, and build a green power system. In recent years, great efforts have been made in the development of smart grids, new energy grid integration, and AC-DC hybrid grid construction, as well as the interconnection of regional power grids and the integration of new energy components into the grid, leading to an increasingly complex power grid structure. While large-scale power grids can improve the operational efciency of power systems, they also make the system structure increasingly complex, bringing many security risks. Among them, the problem of small disturbance stability has become increasingly prominent, as the occurrence of power system oscillations affects the normal power transmission of the grid. In severe cases, it may lead to system separation or even catastrophic largescale blackout accidents, causing heavy losses to national life and social economy. On June 17, 2009, due to a switch explosion accident, multiple interconnection lines of the 500KV main network in the Central China Power Grid experienced varying degrees of power oscillation, resulting in a largescale blackout. Similar incidents have also occurred internationally. On January 23, 2023, the power grid in Pakistan experienced continuous oscillations, triggering the separation of the northern and southern power grids, ultimately leading to a nearly 22hour blackout in most areas, with a power loss of up to 11,356 MW, affecting the lives of 220 million people. Therefore, studying the small disturbance stability of power systems, analyzing damping levels, identifying weak damping modes in a timely manner, and formulating reasonable correction schemes to effectively prevent weak damping oscillations are essential conditions to ensure the safe and stable operation of modern complex and diverse power systems. The N-l operating mode of the power system is a security criterion used to ensure the reliability and stability of the power system. Specically, the N-1 criterion refers to the requirement that under normal operating conditions, when any single component of the power system (such as a generator, transmission line, or transformer) fails or is disconnected due to maintenance needs, the system must be able to maintain stable operation and normal power supply. Other components should not be overloaded, and the system should continue to supply power without experiencing further failures. Under the N-1 operating mode, if a transmission line is overloaded and subsequently disconnected, the redistribution of power ow may lead to cascading failures within the transmission section, increasing system security risks. To ensure the small disturbance stability of the power system, it is necessary to conduct safety assessments and corrections promptly to eliminate line overloads. SUMMARY The purpose of this application is to provide a power system small disturbance stability assessment and correction method and system considering the N-l operating mode, which can prevent possible low-frequency oscillations in the assessed power system during operation and optimize the stability of the assessed power systems grid. This enables the assessed power system's grid to obtain optimized operational data required for the static security and stable operation of the assessed power system under any operating mode, ensuring the safe, stable, and reliable operation of the power grid. To achieve the above purpose, this application provides the following solution: In the rst aspect, this application provides a power system small disturbance stability assessment and correction method considering the Nl operating mode, comprising: Real-time acquisition of operational data of the power system under the N-l operating mode; Determining the minimum damping ratio of the power system and the damping ratio sensitivity index of each generator in the power system using a power sensitivity calculation model based on the acquired operational data; the power sensitivity calculation model is obtained using a random forest algorithm and a gradient boosting decision tree algorithm; the damping ratio sensitivity index represents the sensitivity of active power relative to the damping ratio; Determining whether the minimum damping ratio is greater than or equal to a set stability threshold; If the minimum damping ratio is greater than or equal to the set stability threshold, determining that the power system is small disturbance stable; If the minimum damping ratio is less than the set stability threshold, adjusting the active power of generators in the power system with the objective of minimizing the total variation in active power, based on the damping ratio sensitivity index and constraint conditions, and re-determining the minimum damping ratio of the power system and the damping ratio sensitivity index of each generator in the power system until the minimum damping ratio is greater than or equal to the set stability threshold; the constraint conditions ensure that there is no overload in the transmission lines of the power system. Optionally, the damping ratio sensitivity index of the generator is determined using the following formula: wherein, i is the generator number, j is the load node number, is the damping ratio sensitivity index of the i-th generator, is the active power change of the line between the ith generator and the jth load node, is the active power change of the ith generator, and the size of satises the upper and lower limits of the active power of the generator. Optionally, the active power change of the line between the ith generator and the jth load node is determined by the following formula: wherein, 11 is the total number of generators in the power system. Optionally, when correcting the active power of the generators in the power system based on the damping ratio sensitivity indices and constraint conditions, the objective is: wherein, is the target value, is the minimum operator, is the positive value of the active power change of the i-th generator, is the negative value of the active power change of the i-th generator, and n is the total number of generators in the power system. Optionally, the constraint conditions include: damping ratio constraints, constraints between the total damping ratio variation of the power system and the active power variation of each generator, equality constraints, and inequality constraints; the equality constraints include the power ow equations of each node in the power system; the inequality constraints include node voltage constraints, generator output constraints, line ow constraints, and transmission section constraints. Optionally, the damping ratio constraint is: ; wherein, go is the minimum damping ratio corresponding to the power system under the initial operation mode, is the total damping ratio change of the power system, and is the set threshold; the constraint between the total damping ratio change of the power system and the active power change of each generator is: wherein, i is the generator number, is the damping ratio sensitivity index of the i-th generator, is the active power change of the i-th generator, is the total damping ratio change of the power system, and n is the total number of generators in the power system. Optionally, the power ow equations of each node in the power system are: wherein, i is the generator number, j is the load node number, is the active power of the ith generator, is the reactive power of the ith generator, is the active power of the jth load node, is the reactive power of the jth load node, and ff is the voltage amplitude of the ith generator; is the voltage amplitude of the jth load node, is the element amplitude of the admittance matrix between the ith generator and the jth load node, , are the phase angles of the voltage of the ith generator, is the phase angle of the voltage of the j th load node, is the element phase angle of the admittance matrix between the i th generator and the jth load node, is the system node set, and the system node set is the set of generators and load nodes in the power system. Optionally, the node voltage constraint is: wherein, is the upper limit of the voltage amplitude of the i-th generator; is the lower limit of the voltage amplitude of the ith generator, and is the voltage amplitude of the i-th generator; the unit output constraint is: ; wherein, is the active power of the i-th generator, is the active power of the j-th load node, is the lower limit of the active power of the i-th generator, and is the upper limit of the active power of the i-th generator; is the lower limit of the active power of the j- th load node, is the upper limit of the active power of the jth load node, is the generator node set, and the generator node set is the set of generators in the power system; is the set of load nodes, and load node set is the set of load nodes in the power system; the line power ow constraint is: wherein, is the lower limit of the line power between the i-th generator and the j-th load node, is the upper limit of the line power between the i-th generator and the j-th load node, and is the active power of the line between the i-th generator and the j-th load node. optionally, the transmission section constraint is: ; wherein, is the active power of the line in the transmission section before the active power of the generator is corrected, is the active power of the line in the transmission section after the active power of the generator is corrected, is the maximum power flow allowed to pass through the transmission section when the power system is operating normally, m is the total number of lines in the transmission section, is the transmission section line set, the transmission section line set is the set of lines in the transmission section of the power system, is the active power change of the lines in the transmission section after the active power of the generator is corrected, 1 is the line included in the transmission section, is the damping ratio sensitivity index of the generator in the transmission section, and is the active power change of the generator in the transmission section. Furthermore, this invention provides a power system small-disturbance stability assessment and correction system considering the N-l operating mode, characterized in that the power system small-disturbance stability assessment and correction system considering the N-1 operating mode includes: a data acquisition module, used for real-time acquisition of operating data of the power system under the N-l operating mode; a damping ratio calculation module, used for determining the minimum damping ratio of the power system and the damping ratio sensitivity index of each generator in the power system by using a power sensitivity calculation model based on the operating data; the power sensitivity calculation model is obtained using a random forest algorithm and a gradient boosting decision tree algorithm; the damping ratio sensitivity index represents the sensitivity of active power with respect to the damping ratio; a judgment module, used for determining whether the minimum damping ratio is greater than or equal to the preset stability threshold; a small-disturbance stability assessment module, used for determining that the power system is small-disturbance stable if the minimum damping ratio is greater than or equal to the preset stability threshold; a correction control and damping ratio prediction module, used for adjusting the active power of generators in the power system based on the damping ratio sensitivity index and constraint conditions when the minimum damping ratio is less than the preset stability threshold, with the objective of minimizing the total variation of generator active power, and for redetermining the minimum damping ratio of the power system and the damping ratio sensitivity index of each generator in the power system until the minimum damping ratio is greater than or equal to the preset stability threshold; the constraint conditions ensure that there is no overload in the lines of the power system. According to the specic embodiments provided in this application, the following technical effects are disclosed: This application provides a small disturbance stability assessment and correction method and system for power systems considering the Nl operating mode. For systems in weak damping modes under the Nl operating mode, the method minimizes the total variation in active power of the generators as the objective and adjusts the active power of the generators based on the damping ratio sensitivity index and constraint conditions. This can improve the systems minimum damping ratio, ensuring that the damping ratio reaches above the set stability threshold, thereby ensuring stable operation of the power system. The obtained correction scheme can be input into the RF-GBDT model, which can accurately estimate the corrected damping ratio. This application can prevent possible low-frequency oscillations in the assessed power system during operation and perform stability optimization calculations for the assessed power systems grid. It enables the assessed power systems grid to obtain optimized operational data required for the static security and stable operation of the power system under any operating mode. The grid operation optimization data can be used for automatic calculation and verication, and the verication results can directly guide the formulation of the power systems static security and stability grid operation mode, ensuring the safe, stable, and reliable operation of the grid. BRIEF DESCRIPTION OF THE FIGURES In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the drawings required for use in the embodiments will be briey introduced below. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this eld, other drawings can also be obtained based on these drawings without creative work. Figure 1 is a ow chart of a method for evaluating and correcting small disturbance stability of a power system considering N-l operation mode in an embodiment of the present application; Figure 2 is a functional module diagram of a system for evaluating and correcting small disturbance stability of a power system considering Nl operation mode provided by an embodiment of the present application; Figure 3 is a system structure topology diagram of the case IEEE39 provided by another embodiment of the present application; Figure 4 is a system correction control ow chart of the case IEEE39 provided by another embodiment of the present application; Figure 5 is a system damping ratio prediction scatter plot of the case IEEE-39 provided by another embodiment of the present application. DETAILED DESCRIPTION OF THE INVENTION The following will combine the drawings in the embodiments of the present application to clearly and completely describe the technical solutions in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this eld without creative work are within the scope of protection of the present application. The terms involved in this application are explained as follows: Data-driven: It is to collect massive amounts of data through mobile Internet or other related software, organize the data into information, and then integrate and rene the relevant information, and form an automated decision-making model through training and tting based on the data. When a new situation occurs and new data is input, the system can use the previously established model to make decisions directly in an articial intelligence manner. It is closely integrated with digital transformation. The fundamental purpose of digital transformation is to promote business growth through new technologies such as big data, articial intelligence, cloud computing, and mobile Internet. Articial intelligence: It is a branch of computer science that attempts to understand the essence of intelligence and produce a new intelligent machine that can respond in a similar way to human intelligence. Research in this eld includes robots, language recognition, image recognition, natural language processing, and expert systems. Since the birth of articial intelligence, the theory and technology have become increasingly mature, and the application eld has been continuously expanded. It can be imagined that the technological products brought by articial intelligence in the future will be the "container" of human wisdom. Articial intelligence can simulate the information process of human consciousness and thinking. Articial intelligence is not human intelligence, but it can think like humans and may also exceed human intelligence. Machine learning: Use algorithms to learn from massive amounts of data, nd out the rules, and predict the development trend in the future through data. N-l operation mode: Below the given tie line total active limit, disconnect any line in the group of tie lines, and the ow of the remaining lines will not be overloaded. RF-GBDT algorithm: This is a machine learning algorithm that combines Random Forest (RF) and Gradient Boosting Decision Trees (GBDT). Random Forest is an ensemble learning method that constructs multiple decision trees and combines their prediction results to improve the models generalization ability and accuracy. Gradient Boosting Decision Tree is a boosting method that minimizes the gradient of the loss function by adding trees step by step, thus improving the models performance. The RF- GBDT algorithm is capable of handling various types of data, including high- dimensional, sparse features, and nonlinear relationships, and can address complex problems. Power ow calculation: This refers to the calculation of voltage, current magnitudes and directions, and power distribution in a power system under a specied operating mode and connection conguration, from the power sources to the load points. Power ow constraints: These refer to the constraints in the power ow, with static stability being a limiting factor in the power ow. With the development of articial intelligence technology, more and more new algorithms are being proposed and applied in various elds of power systems. The most widely applied machine learning algorithms are those based on Support Vector Machines (SVM) and Neural Networks. In the existing technology, a large number of machine learning algorithms have been used to implement conventional small disturbance stability assessments and corrections in power systems. However, small disturbance stability assessments and corrections for power systems considering the N-l operating mode mainly use computer programming methods, and the use of machine learning algorithms is relatively rare. The existing technology involves solving the systems state equations to obtain the minimum damping ratio, which has the disadvantage of requiring high computer memory, complicated programming, and large computational load. The technical problem to be solved by this application is the small disturbance stability assessment and correction method and system for power systems considering the Nl operating mode. By adjusting the active power output of the generators to correct the weak damping mode operation of the power system, this is an important preventive control measure for the actual grid operation. This application uses articial intelligence methods to perform small disturbance stability assessment for power systems considering the Nl operating mode. The Phasor Measurement Unit (PMU) can acquire electrical quantities such as active and reactive power from loads, as well as the active and reactive power output from generators, providing reliable data support for remote control of power system security and stability. Machine learning algorithms can mine and process data to uncover potential rules and features of grid operation, dynamically monitoring the power systems performance. This enables machine learning algorithms to assess the small disturbance stability of the power system, and then use the damping ratio sensitivity index to identify key factors affecting small disturbance stability. This provides very valuable power ow control guidance information for dispatchers. Therefore, a sensitivity analysis-based method is used to address the small disturbance stability correction issue. This method takes the minimum adjustment of generator output or the generation cost as the objective function, and under the premise of satisfying the specied constraints, calculates the sensitivity relationship between line power and generators. During the process of adjusting the active power output of each generator, if the control variable exceeds its limit, the control variable is redistributed according to the branch constraints until the limit is removed, thus achieving the small disturbance stability assessment and correction for the power system considering the N- 1 operating mode. First, an N-l operation mode small disturbance stability assessment model for the power system is established. This requires acquiring and constructing a dataset for analyzing the small disturbance stability of the system. By writing programs for power ow and small disturbance stability, a dataset for articial intelligence algorithms is generated. In this application, the RF-GBDT algorithm, which has high prediction accuracy and fast convergence speed, is used to perform a nonlinear mapping of system operating parameters and the minimum damping ratio, estimating the minimum damping ratio during system operation. Then, it is determined whether the system is in a weak damping state. If it is in a weak damping state, the sensitivity index between the systems minimum damping ratio and the active power output of the generators is constructed. The damping ratio sensitivity index is used to determine the units to be adjusted and to determine the adjustment amount of the participating units. Active power modulation takes the damping ratio sensitivity of each generator as a reference, and the adjustment amount is distributed to each generator according to their weight, or the number of adjusted units is controlled, and combinations of generators are constructed. The upper and lower adjustment amounts of each generators active power are determined, and the modulation amount is set to the smallest active power change. This application, on the one hand, does not require solving the systems state equations to obtain the systems minimum damping ratio. On the other hand, it overcomes the limitations of existing control methods, which may require selecting additional parameters (such as load power, reactive power compensation devices, etc.) for correction, and may easily result in adjustment limitations. To make the above objectives, features, and advantages of this application clearer and easier to understand, the following provides a detailed explanation of this application with reference to the accompanying drawings and specic embodiments. In an exemplary embodiment, as shown in Figure 1, a small disturbance stability assessment and correction method for a power system considering the N-l operation mode is provided, which includes: Real-time acquisition of operating data of the power system under the N-1 operation mode. Based on the acquired operating data, a power sensitivity calculation model is used to determine the minimum damping ratio of the power system and the damping ratio sensitivity index of each generator in the system; the power sensitivity calculation model is obtained using the Random Forest (RF) algorithm and the Gradient Boosting Decision Tree (GBDT) algorithm; the damping ratio sensitivity index is the sensitivity of active power relative to the damping ratio. Determine whether the minimum damping ratio is greater than or equal to the set stability threshold. If the minimum damping ratio is greater than or equal to the set stability threshold, the power system is determined to be small disturbance stable. If the minimum damping ratio is less than the set stability threshold, the active power change sum of the generators is minimized as the objective. The active power of the generators in the power system is corrected according to the damping ratio sensitivity index and constraint conditions, and the minimum damping ratio of the power system and the damping ratio sensitivity index of each generator in the system are recalculated, until the minimum damping ratio is greater than or equal to the set stability threshold; the constraint condition is that no overload occurs in the lines of the power system. In an exemplary embodiment, the active power of the line of the power system is obtained according to the load power and the generator power, that is, , 0 wherein, is the active power of the ith load node, is the reactive power of the j-th load node, is the active power of the ith generator, is the reactive power of the i-th generator, and is the active power of the line between the ith generator and the j-th load node. In an exemplary embodiment, the damping ratio sensitivity index of the generator is determined using the following formula: wherein, i is the generator number, j is the load node number, is the damping ratio sensitivity index of the i-th generator, is the active power change of the line between the i-th generator and the j-th load node, is the active power change of the i-th generator, and the size of satises the upper and lower limits of the active power of the generator. In an exemplary embodiment, the active power change of the line between the i-th generator and the j -th load node is determined using the following formula: wherein, n is the total number of generators in the power system. In an exemplary embodiment, the goal of correcting the active power of the generator in the power system according to the damping ratio sensitivity index and the constraint condition is: wherein, is the target value, is the minimum operator, is the positive value of the active power change of the i-th generator, is the negative value of the active power change of the i-th generator, and n is the total number of generators in the power system. In an exemplary embodiment, the constraints include: damping ratio constraints, constraints between the total damping ratio change of the power system and the active power change of each generator, equality constraints and inequality constraints; the equality constraints include the power ow equations of each node in the power system; the inequality constraints are network physical constraints and operation constraints, including node voltage constraints, unit output constraints, line power ow constraints and transmission section constraints. In an exemplary embodiment, when a small disturbance causes the system to oscillate at a low frequency, adjusting the active output of the generator can improve the stability of the system. In order to ensure the stable operation of the power system Nl operation mode, an appropriate correction control method is used to increase the system operation damping ratio so that the system damping ratio is greater than the set threshold {limit. The damping ratio constraint is: wherein, £0 is the minimum damping ratio corresponding to the power system under the initial operation mode, is the total damping ratio change of the power system, and is the set threshold. The constraint between the total damping ratio change of the power system and the active power change of each generator is: wherein, , i is the generator number, is the damping ratio sensitivity index of the i-th generator, is the active power change of the i-th generator, is the total damping ratio change of the power system, and n is the total number of generators in the power system. In an exemplary embodiment, the power ow equations of each node in the power system are: wherein, i is the generator number, j is the load node number, is the active power of the i-th generator, is the reactive power of the i-th generator, is the active power of the j-th load node, is the reactive power of the j-th load node, and ff is the voltage amplitude of the i-th generator; is the voltage amplitude of the j-th load node, is the element amplitude of the admittance matrix between the i-th generator and the j-th load node, , are the phase angles of the voltage of the i-th generator, is the phase angle of the voltage of the j -th load node, is the element phase angle of the admittance matrix between the i- th generator and the j -th load node, is the system node set, and the system node set is the set of generators and load nodes in the power system. In an exemplary embodiment, the value of the node voltage constraint is related to the voltage level, the type of node, the region, or the normal or emergency condition of the node. The node voltage constraint is: wherein, is the upper limit of the voltage amplitude of the ith generator; is the lower limit of the voltage amplitude of the ith generator, and is the voltage amplitude of the ith generator; The group output limit includes active output limit and reactive output limit. The group output constraint is: wherein, is the active power of the ith generator, is the active power of the j -th load node, is the lower limit of the active power of the i-th generator, and is the upper limit of the active power of the ith generator; is the lower limit of the active power of the j- th load node, is the upper limit of the active power of the jth load node, is the generator node set, and the generator node set is the set of generators in the power system; is the set of load nodes, and load node set is the set of load nodes in the power system; the line power ow constraint is: wherein, is the lower limit of the line power between the i-th generator and the j-th load node, is the upper limit of the line power between the i-th generator and the j-th load node, and is the active power of the line between the i-th generator and the j-th load node. In an exemplary embodiment, section management in a power system is one of the key links to ensure stable, safe and efcient operation of the power system. By constraining the section, the problem of small disturbance instability in the power system can be prevented and controlled. The transmission section constraint is: wherein, is the active power of the line in the transmission section before the active power of the generator is corrected, is the active power of the line in the transmission section after the active power of the generator is corrected, is the maximum power flow allowed to pass through the transmission section when the power system is operating normally, m is the total number of lines in the transmission section, is the transmission section line set, the transmission section line set is the set of lines in the transmission section of the power system, is the active power change of the lines in the transmission section after the active power of the generator is corrected, 1 is the line included in the transmission section, is the damping ratio sensitivity index of the generator in the transmission section, and is the active power change of the generator in the transmission section. This embodiment scheme uses articial intelligence algorithms for rapid small disturbance stability assessment and correction control of the power system considering the N-l operation mode, breaking through the challenges faced by previous computer programming technologies, such as limitations in content capacity and long calculation times. The overall workow of the small disturbance stability assessment and correction method for the power system considering the N-l operation mode in the above embodiment includes the following steps: Step 1: Acquire real-time operational data of the system in the N-l operation mode, mainly including system state variables and control variables, such as the voltage magnitude and phase angle of PQ nodes, reactive power and phase angle of PV nodes, active and reactive power of load nodes, and the voltage and phase angle of balance nodes. Step 2: Based on the parameters of all nodes, use the power ow program to calculate the real-time operating data, thereby obtaining the power ow data of the system in the N-1 operation mode (e. g., the transmission power of each line). Step 3: Choose an appropriate RF-GBDT algorithm model and form an articial intelligence model dataset from the collected data for training. Use the calculated transmission power data of each line of the system to train the RF-GBDT algorithm model, obtaining the relationship between the input and output in the dataset as the power sensitivity calculation model. The inputs are system state variables and control variables, and the output is the systems minimum damping ratio. Adjust the models parameters to ensure that the systems damping ratio evaluation is as accurate as possible. Step 4: Based on the power systems topology, set the N-l fault set, which can cover the impact of disconnection of branches with large power ows under normal conditions on the network topology. This is used to determine the systems transmission sections and the transmission limits of these sections. Step 5: In the trained power sensitivity calculation model, use numerical perturbation methods to estimate the approximate sensitivity of power. In the determined operating mode, check whether the remaining lines in the Nl condition can overload (if the minimum damping ratio is less than the set stability threshold). If there is overload, start the correction control program. Step 6: Start the correction control program, with the objective function being the minimization of the total active power of the generators and the minimum generation cost. The constraints include the upper and lower limits of the active and reactive power of the generators, the upper and lower limits of node voltages, and active power constraints on the transmission section. Optimize and adjust the active power of the generators to eliminate line overloads, while ensuring that no new overloads occur. Step 7: Check the calculation results in the corrected output le and generate a report. This result ensures that the active power ow of the transmission section under the static security power ow constraints of the N-l operation mode is within a safe range and is in a stable operating mode. This operating mode of the grid is the safety and stability operating limit of the evaluated power system. This application processes the real-time operating data of the current power system using the machine learning RF-GBDT algorithm, establishing the mapping relationship between inputs and outputs. It uses the ofine established data-driven model to predict and assess the small disturbance stability of the power system under the N-1 operation mode, while estimating the approximate damping ratio sensitivity of each generator. If the damping ratio is greater than the set stability threshold, the system is small disturbance stable. If the damping ratio is less than the set stability threshold, the system is in a weak damping or unstable operating state. The weak damping mode affects the small disturbance stability of the power system, and the active power of the generators needs to be modulated. The adjustment amount of active power is determined by the optimization algorithm to raise the damping ratio above the stability threshold. A correction control optimization model is established based on the set stability threshold and sensitivity, and the optimized adjustment strategy is used to regulate the active output of the generators, ensuring the safe and stable operation of the system. Compared with the existing technology, this application has the following benecial effects: 1. It can prevent lowfrequency oscillation situations that may occur during the operation of the evaluated power system and can perform stability optimization calculations for the power grid of the evaluated power system, ensuring that the power grid of the evaluated power system can obtain the optimized operation mode data required for static safety and stable operation under any operating mode. It can also use the optimized grid operation mode data for automatic calculation and verication, and the verication results can directly be used to guide the compilation of the evaluated power systems static safety and stability grid operation mode to ensure the safe, stable, and reliable operation of the grid. 2. It can make the formulation of the grids static voltage stability operation mode simpler and easier, shorten the workow and formulation time, reduce the workload and pressure on operating personnel, and comprehensively improve the voltage quality and safety stability of the grid. Based on the same inventive concept, this application embodiment also provides a small disturbance stability evaluation and correction system for the power system considering the N-1 operation mode. The solution provided by the system for solving the problem is similar to the implementation solution described in the above method, so the specic details in the one or more embodiments of the small disturbance stability evaluation and correction system for the power system considering the N-l operation mode can be referred to the above description of the small disturbance stability evaluation and correction method for the power system considering the N-1 operation mode, and will not be repeated here. In an exemplary embodiment, as shown in Figure 2, the small disturbance stability evaluation and correction system for the power system considering the N-1 operation mode includes: Data Acquisition Module: Used to acquire real-time operational data of the power system in the N-l operation mode. Damping Ratio Calculation Module: Used to determine the minimum damping ratio of the power system and the damping ratio sensitivity indicators of each generator in the power system according to the operation data by adopting the power sensitivity calculation model. The power sensitivity calculation model is obtained by using the random forest algorithm and gradient boosting decision tree algorithm. The damping ratio sensitivity indicator is the sensitivity of active power to the damping ratio. Judgment Module: Used to judge whether the minimum damping ratio is greater than or equal to the set stability threshold. Small Disturbance Stability Evaluation Module: Used to determine that the power system is small disturbance stable if the minimum damping ratio is greater than or equal to the set stability threshold. Correction Control and Damping Ratio Prediction Module: Used to correct the active power of the generators in the power system if the minimum damping ratio is less than the set stability threshold, with the objective of minimizing the total change in active power, and based on the damping ratio sensitivity indicators and constraints, and then redene the minimum damping ratio and the damping ratio sensitivity indicators for each generator until the minimum damping ratio is greater than or equal to the set stability threshold. The constraints are the conditions that prevent overload in the systems lines. This embodiment obtains operational data such as load power, line power, generator output, and minimum damping ratio for a system containing small hydropower. Based on the collected data, a dataset is formed to train the articial intelligence model. An appropriate articial intelligence model is selected to establish the relationship between input and output in the dataset, and the model parameters are adjusted to achieve good evaluation results. The minimum damping ratio of the system is estimated to implement small disturbance stability evaluation. Damping ratio constraints, power balance constraints, and constraints between the total damping ratio variation of the system and the active power variations of each generator are adopted as constraint conditions. The objective function is to minimize the sum of squared changes in the generators active power, optimizing and correcting the active power variations of the generators. The corrected damping ratio is predicted based on the model established in the small disturbance stability evaluation module. Taking the IEEE-39 node system as an example, the system structure topology is shown in Figure 3. A real-time low-frequency oscillation operation analysis and optimal correction control are conducted under the N-l condition for the system. The analysis steps are as follows: 1. The system has 39 buses, 10 generators, and 46 transmission lines. The buses are numbered 1-39, and G represents the generators. 2. Obtain the operational data of the system's generator output, load power output, etc. 3. Randomly uctuate the system load between 70% and 130%, with the generators active and reactive power uctuating by 30%, ensuring power balance in the system. Power ow calculations are performed using the power ow program to generate a large amount of raw data, forming the dataset. 4. Train the RFGBDT algorithm model using the generated large dataset, adjusting the model parameters to achieve better evaluation results. The relationship between the generator output and line power is obtained, and the damping ratio sensitivity is estimated with high accuracy. 5. Under a given operating mode, evaluate the line power situation after the disconnection of any line under the Nl condition. If the line is overloaded, the correction control program is initiated. 6. Establish a correction control optimization model (i.e., the small disturbance stability evaluation model and correction model in Figure 4). The process follows the reference shown in Figure 4. The active power of controllable generators in the system is perturbed, damping ratio sensitivity is calculated, and the generators active power is optimized. 7. Review the calculated results after correction, output the calculation result report, which ensures that the evaluated power system is in a safe and stable operating mode. This operating mode is the safe and stable operation limit of the evaluated power systems grid. Here is an example to explain: In the operation of the IEEE-39 node system, the active power security and correction control effects of the evaluated power system in this embodiment are very signicant. This application uses the RF-GBDT algorithm to construct the power sensitivity calculation model. According to the Nl principle, transmission line disconnection faults are simulated, considering the uctuations in generator and load power. A total of 10,000 different operating points considering various N-l line fault scenarios are formed, creating a dataset of 10,000 samples. MAPE (Mean Absolute Error) and RMSE (Root Mean Square Error) are used as error measures to represent the accuracy of the prediction results. Please refer to Figure 4. The set stability threshold is 0.03, and the correction process shown in Figure 4 is used for correction. The prediction results are shown in Table 1. Overall, the models error values are still relatively small, with high accuracy, making it suitable for estimating damping ratio sensitivity. Table 1. Prediction results of MAPE and RMSE The given system initial state does not meet the small disturbance stability check under the Nl operation mode. The damping ratio sensitivity results of each generator estimated by the RFGBDT model are shown in Table 2, where the G1 unit is set as the system's balancing unit, does not participate in active modulation, and has a sensitivity of 0. Table 2 The damping ratio sensitivity results of each generator estimated by the RF- GBDT model Then, the generator active power adjustment is obtained according to the estimated sensitivity, and the system optimization correction control is performed. The process and results of the generator active power modulation are shown in Table 3. Table 3 The process and results of the generator active power modulation The above example illustrates that under the premise of a certain network structure, when the system cannot meet the small disturbance stability under the N-l operating mode, in order to improve the small disturbance stability of the system, the active output of the generator set can be adjusted. For the system in the weak damping mode under the N-1 operating mode, the correction control method proposed in this application can be used to improve the minimum damping ratio of the system, so that the damping ratio reaches above the set stability threshold, ensuring the stable operation of the power system, and the obtained correction scheme is brought into the RF-GBDT algorithm. As shown in Figure 5, the corrected damping ratio can be estimated more accurately. The formulation of its scheme can adopt a data-driven scheme to generate a real-time control strategy based on the specic input data situation. The above describes the implementation method of the present application in conjunction with the accompanying drawings, explores the application of generator output adjustment measures in active safety correction control, and makes some meaningful research on active operation risk correction control combined with sensitivity method and operation risk assessment. However, due to the complexity of the active operation risk control of the power grid, it is not limited by the above implementation case when implemented, and ordinary technicians in this eld can make various changes or modications within the scope of the attached claims. The technical features of the above embodiments can be combined arbitrarily. To make the description concise, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specication. This article uses specic examples to illustrate the principles and implementation methods of this application. The description of the above embodiments is only used to help understand the method and core idea of this application. At the same time, for general technicians in this eld, according to the idea of this application, there will be changes in the specic implementation method and application scope. In summary, the content of this specication should not be understood as a limitation on this application. -21-
Claims
1. Method for assessing and correcting the stability of the electricity grid in case of minor disturbances, taking into account the NL operating mode, characterized by the method for assessing and correcting stability of the electricity grid in the event of minor disruptions, taking into account the Nl business mode, the following includes: real-time acquisition of operating data from the electricity grid in the Nl-operating mode; based on the company data, using a model for the calculation of the power sensitivity to determine the minimum damping ratio of the power grid and the sensitivity indices for the damping ratio of each generator in the electricity grid; where the model for calculating the power sensitivity is obtained using a random forest algorithm and a gradient boosting decision tree algorithm; where the sensitivity index for the damping ratio the sensitivity of the active represents power versus damping ratio; determining whether the minimum damping ratio is greater than or equal to the preset stability threshold value; where if the minimum damping ratio is greater than or equal to the preset stability threshold value, the power grid is considered as stable under small disturbances; where if the minimum damping ratio is less than the preset stability threshold value, with the aim of measuring the total change in active power of the generators to minimize the active power of the generators in the electricity grid is corrected based on the sensitivity indices and the boundary conditions of the damping ratio, and where the minimum power grid damping ratio and sensitivity indices of the -22- damping ratio of each generator in the grid can be re-established determined until the minimum damping ratio is greater than or equal to the preset stability threshold value; where the boundary conditions for this ensure that there is no overload in the electricity grid lines.
2. Method for assessing and correcting the stability of the electricity grid in case of minor disruptions, taking into account the NL operating mode according to claim 1, characterised in that the sensitivity index of the Damping ratio of the generator is determined using the following formula: C,- = & ; AB where i is the generator number, j is the tax node number, Ci is the sensitivity index of the damping ratio of the i-th generator, APÙ' de change in the active power of the line between the i-th generator and the j-th tax node, AB the change in active power of the i-th generator and the size of AB satisfies the upper and lower bounds of the active power of the generator.
3. Method for assessing and correcting the stability of the electricity grid in case of minor disruptions, taking into account the Dutch operating mode according to claim 2, characterised in that the change of the active power of the line between the ith generator and the jth load node is determined by the following formula: AB,- =C1AR+C2APz +"'+Cr1APn; where n is the total number of generators in the power system. -23- 4. Method for assessing and correcting the stability of the electricity grid in case of minor disruptions, taking into account the NL operating mode according to claim 1, characterised in that when correcting the active power of the generators in the electricity grid based on the sensitivity indices of the damping ratio and the limiting conditions, the goal is: f(x) = min[Z(APá + APG?» ; [:l . ' . . . + where f(x) is the target value, m1n[ ] is the minimum operator, APG is the positive value of the change of the active power of the i-th generator, APG" the negative value of the change in active power of the i-th generator is and n is the total number of generators in the electricity grid.
5. Method for assessing and correcting the stability of the electricity grid in case of minor disruptions, taking into account the NL operating mode according to claim 1, characterised in that the restriction conditions include: limitations on the damping ratio, limitations between the total variation of the damping ratio of the power grid and the variation of the active power of each generator, equality constraints and inequality constraints; where the equality constraints are the power flow equations of each node in the electricity grid; the inequality constraints restrictions for the node voltage, generator power restrictions, restrictions for the line current and restrictions for the transmission section.
6. Method for assessing and correcting the stability of the electricity grid in case of minor disruptions, taking into account the Dutch operating mode according to claim 5, characterised in that the limitation for the damping ratio is: -24- fo +Af Z Óimit; where &G is the minimum damping ratio corresponding to the energy system in the initial operating mode, A98 the total change in the damping ratio of the power system is and 98 the set threshold value is; the limitation between the total change in the damping ratio of the power system and the change in active power of each generator is: 2am = Ag - [=1 where i is the generator number, Ci is the sensitivity index of the damping ratio of the i-th generator is, AB is the change of the active power of the i-th generator is, A5 is the total change in the damping ratio of the power system is and n is the total number of generators in the energy system is.
7. Method for assessing and correcting the stability of a small disturbance system in the electricity grid, taking into account the Nloperating mode, according to claim 5, wherein the power flow equations of each node in the electricity grid are: Pa _PL / _ Z KEV / 003517 =O "ES 1 your S - . 9 N , QGi QL. / _ Z ViY-VJ 5111547 = 0 jeSA, where i is the generator number, j is the load node number, P Gi is the active power of the i-th generator is, QGÍ is the reactive power of the i-th generator is, PLJ' is the active power of the j-th load node, -25- QLJ is the reactive power of the jth load node, and ff is the voltage amplitude of the i-th generator is; Vf is the voltage amplitude of the j-th load node is, YU is the element amplitude of the admittance matrix between the i-th generator and the j-th load node is, either! 25" _51' _a; where 5i is the phase angles of the voltage of the i-th generator are, 51 the phase angle of the voltage of the jth load node is, ff is the element phase angle of the admittance matrix between the i-th generator and the j-th load node is, SN is the system node set is and the system node set SN is the set of generators and load nodes in the electricity grid.
8. Method for assessing and correcting the stability of the electricity grid in case of minor disruptions, taking into account the NL operating mode, according to claim 5, wherein the node voltage constraint is: I / z',minSI / I'SI / I'Jnax iESG; where V is the upper limit of the voltage amplitude of the i-th generator; V is the lower limit of the voltage amplitude of the i th generator, and Vide voltage amplitude of the i th generator is; where the unit output constraint is: PGi,min £ fa S PGí,mwc iE SG, - . PLj,min S Hi S PLjmwc ] E SL ' where PGi is the active power of the ith generator, PLf is the active power is of the j-th load node, Pal-min is the lower limit of the active power of the i-th generator, and Pc,-,, is the upper limit of the active power of the i-th generator; H is the lower limit of the active power of the j-th load node, [DLJ is the upper limit of the active power of the j-th load node, SG is the generator node set and the generator node set SG is the set of generators in the electricity grid; SL is the set load nodes is and the load node set SL is the set load nodes in the electricity grid; where the grid current limitation is: Pij,min£F1)'j£Pij,max iESLI- where B is the lower limit of the line power between the i-th generator and the j-th load node, Pff," is the upper limit of the line power between the i-th generator and the j-th load node, and Pff is the active power of the line between the i-th generator and the j-th load node.
9. Method for assessing and correcting the stability of the electricity grid in case of minor disruptions, taking into account the Dutch operating mode, according to claim 5, wherein the transmission section restriction is: ZH 53 lesson; l=1 AB =C1AR+C2AP2 +---+CmAPmr' B = BO + AB ; 0 where Pl is the active power of the line in the transmission section before the active power of the generator is corrected, Pl the active power of _27_ the line in the transmission section is after the active power of the generator is corrected, Pi is the maximum energy flow allowed through the transmission section currents when the power system is operating normally, m the total number of lines in the transmission section is, S is the transmission section line set, the transmission section line set S the set of lines in the transmission section of the power system is, API the change of the active power of the lines in the transmission section is after the active power of the generator is corrected, I is the line included in the transmission section, C1,C2---C the sensitivity index of the damping ratio of the generator in the transmission section and ABAP?" ' 'AP' the change of the active power of the generator in the transmission section.
10. System for assessing and correcting the stability of the electricity grid in case of minor disturbances, taking into account the Nl operating mode, characterized because the system for assessing and correcting the stability of the electricity grid in case of minor disturbances, taking into account the NL operating mode, the following includes: a data acquisition module, which is used for real-time acquisition of operating data of the electricity grid in the Nl operating mode; a module for calculating the damping ratio, which is used for determining the minimum damping ratio of the electricity grid and the sensitivity index of the damping ratio of each generator in the electricity grid using a model for calculating the asset sensitivity based on the company data; where the model for the calculation of the power sensitivity is obtained using a random forest algorithm and a gradient boosting decision tree algorithm; where the sensitivity index of the damping ratio is the sensitivity of the represents active power versus damping ratio; an assessment module, which is used to determine whether the minimum damping ratio is greater than or equal to the preset stability threshold value; a module for assessing the stability of the electricity grid at small disturbances, used to determine whether the electricity grid is stable for small disturbances if the minimum damping ratio is greater than or equal to to the preset stability threshold value; a correction control and damping ratio prediction module, which uses is used to adjust the active power of generators in the electricity grid based on the sensitivity index and the restriction conditions of the damping ratio when the minimum damping ratio is lower than the preset set stability threshold value, with the aim of reducing the total variation in the active to minimize the power of the generator, and to ensure the minimum damping ratio of the power grid and the sensitivity index of the damping ratio of each generator in the electricity grid to be re-determined until the minimum damping ratio is greater than or equal to the preset stability threshold value; whereby the restriction conditions ensure that there is no overload occurs in the electricity grid lines. 1 / 5 Figure1