Research On Static Voltage Stability Evaluation Method Of Power System Based On Ambient Excitation

With the rapid development of social economy,the scale,complexity and unstable factors of power system are increasing day by day,the load demand of power grid is also gradually increasing,and the operation state of power system is also constantly approaching the stability limit.The traditional analysis method based on modeling and simulation will be affected by model constraints and other factors when facing modern power system,and the parameters are difficult to measure directly,which cannot meet the requirements of timeliness for online analysis of system stability.With the wide application of Wide Area Measurement System(WAMS)in power grid,a large number of real-time measurement data collected provide the feasibility of data-driven power system stability analysis.Therefore,carrying out data-driven static voltage stability assessment of power system is of great significance to ensure the safe and stable operation of power grid.Based on the random response data,this thesis studies the static voltage stability evaluation method of power system under ambient excitation.The specific contents are as follows:Firstly,this thesis briefly introduces the basic principle of wide-area measurement system.According to the different disturbances to the system,the measurement signals can be divided into transient response signals and random response signals.The characteristics of random response signal under ambient excitation are analyzed,and the advantages of system static voltage stability analysis based on random response data are analyzed.Then the current commonly used voltage stability analysis methods and evaluation indicators are described,their advantages and disadvantages are analyzed,and the voltage stability mechanism is deeply studied.Secondly,a sensitivity index based on load bus voltage and reactive power is constructed in this thesis.Combined with the equivalent line model of the system,the feasibility of the bus sensitivity index is theoretically verified.Then,based on the random response signal under ambient excitation,the characteristics of bus sensitivity indicators are analyzed,and the classification of bus sensitivity indicators is proposed: positive sensitivity indicators and negative sensitivity indicators,which can be used to simultaneously monitor the static voltage stability of power system.The simulation results of IEEE 3-machine 9-bus system and IEEE 10-machine39-bus system verify the feasibility and effectiveness of the bus sensitivity index.Finally,in order to improve the accuracy of power system static voltage stability assessment,a method of outlier elimination based on K-Means clustering algorithm is proposed to solve the problem of outliers in the value of bus sensitivity index.In this outlier elimination method,Euclidean distance is used to measure the similarity between the sample data.After the outliers of bus sensitivity are eliminated by K-Means clustering algorithm,the weighted average value(WAV)method is used to fit the sensitivity index for online monitoring of static voltage stability of power system.The validity of the outlier elimination method is verified on IEEE3-machine9-bus system and IEEE10-machine 39-bus system respectively.Through comparative analysis,it can be seen that the method proposed in this thesis effectively improves the accuracy of system static voltage stability assessment.