The Transient Stability Assessment Of Power System Based On PMU Data

With the rapid development of the modern communication technology,PMU has a more and more application in the power grid and it can achieve high precision and real-time dynamic information.The modern grid have a variety of operating mode and an uncertainty of operating scene after fault.Especially when the system instability occurs,the current system monitoring device can't judge system stability trend in the effective time,so that the fault extends to a larger scope and causes the overall collapse of the power system.Most of the traditional transient stability assessment is about accident simulation research based on grid model parameter,so that missed the best control time and cannot be applied to on-line prediction.PMU-based measurement data monitoring technology about online stability is more and more important.For the grid instability accident,it reserved a certain control time.Therefore,this article conducts a depth exploration and research about transient stability assessment based on the measured data from the following several aspects:(1)This paper introduces the traditional commonly used methods of transient stability assessment,aiming to analyze the existed defects in practical application,The methods depend on the system model parameters and have large amount of calculation,so that it is not adapted to the online calculation.This paper analyzes it and improve it.(2)This thesis involves real-time short-term transient angle and voltage stability prediction based on PMU measurement data.It has a phase space reconstruction about the measured data first to restore the dynamic characteristics of the original system better.Then,the method of selecting reasonable embedding dimension and delay time is discussed,it will affect the reconstruction consistency of dynamic characteristics about the original system and the reconstructed system.(3)This paper gives the definition of the maximum Lyapunov exponents(MLE)and monitors the stability using the positive and negative of the MLE based on trajectory information.In the modern power system,the installed PMU(phasor measurement unit)device cannot spread to every node of the power system.On-line stability monitoring can not rely on all the nodes status information of the system,the methods of this paper circumvent this limitation.(4)The principle of general least squares estimation about MLE have been given.Compared with the two point method to calculate MLE,it has a better precision.Also,it avoid the influence of the parameter selection based on two point method of calculating the MLE.(5)The effectiveness analyses of transient angle and voltage stability monitoring have been given combined with 10 machines 39 nodes example.The simulation results prove that its timeliness meet the demand of online stability judgement of the large grid.In this paper,the short-term stability monitoring calculate the maximum Lyapunov exponents using the general least squares method based on the measured trajectory,and the phase space reconstruction theory is applied.They make good use of the measured trajectory information and can apply to the engineering practice.