Modeling And Stability Analysis Of Power System With Time Delay

Wide-area damping controller is an important means to suppress the low frequency oscillation which restrict the transmission capacity of interconnected power grids.In this thesis,modeling and stability analysis for the power system whose wide area damping control loop is under the influence of communication delay are presented,which has important theoretical significance and application value for the design of wide-area damping controller and the improvement of stability level of large-scale power system.Aiming at the cyber-physical power system(CPPS)affected by multiple time delays,this thesis has carried out research on modeling methods,a delayed cyber-physical power system(DCPPS)modeling method for small singal stability analysis and control is proposed,and the delay merge properties for DCPPS is given for this modeling method.Based on the existing solution operator discretization with linear multistep(SOD-LMS)method,a DCPPS eigenvalue analysis method based on partial SOD-LMS(PSOD-LMS)method is proposed.This method can be used to solve the eigenvalues of DCPPS,and analyze the influence of time delay on the small singal stability of DCPPS.In this thesis,the processing method of the time-dependent variable is also given in the transient stability simulation of DCPPS.The transient stability simulation of DCPPS is carried out by this method to verify the accuracy of the modeling method.The main works of this thesis are as follows:(1)Modeling of DCPPS with multiple time-delays is carried out.Firstly,a delay differential-algebraic equation model of DCPPS with multiple delays is constructed and transformed into an infinite-dimensional delay differential equation.Then,the infinite-dimensional delay differential equation is transformed into a finite-dimensional delay differential equation model which is convenient for theoretical analysis.Finally,the closed-loop DCPPS with wide-area damping controller is modeled by using this method,so as to facilitate the subsequent eigenvalue analysis.(2)For the closed-loop DCPPS model proposed in the previous part,the time-delay merge properties is proposed based on the eigenvalue equation and eigenvalue sensitivity of the system,respectively.This theorem shows that when the sum of feedback delay and control delay in the closed-loop DCPPS control loop is constant,the corresponding eigenvalue and eigenvalue trends remain unchanged.By using this theorem,the feedback and control delay can be combined into a comprehensive delay in the subsequent eigenvalue analysis,which reduces the number of time delays and improves the computational efficiency.(3)A DCPPS eigenvalue analysis method based on PSOD-LMS method is proposed,aiming at improving the efficiency of SOD-LMS based method..By using these two eigenvalue analysis methods for simulation,it is proved that the computational efficiency of PSOD-LMS method is higher than that of SOD-LMS method.The larger the system scale,the more obvious the improvement of computational efficiency by partial solution operator discretization processing.(4)Transient stability simulation of DCPPS is carried out,and the correctness of multi-delay DCPPS modeling is verified from the perspective of transient stability simulation.Firstly,the user-defined modeling method is introduced,which makes it easy to construct a DCPPS model.Secondly,the specific steps of DCPPS simulation using alternating solution method are given.Then,an approximation method for system variables affected by time delay is given,which enables one to solve the DCPPS.Finally,the transient stability simulation of DCPPS is carried out to verify the correctness of DCPPS modeling.