Research On Time-delay Characteristic Analysis And Stability Control Of Large Scale Power System

The emergence of Wide Area Measurement System(WAMS)provides a solution for the operation and control of large-scale power system.Through network signals based on synchronous measurement by the WAMS system,optimal control provides important assurance for security operation and stability control of large power system.However,there is a problem of time-delay in the measurement of WAMS system.The existence of time-delay will worsen the performance of the wide area controller and greatly affect the safe and stable operation of the large power system.At present,the time-delay characteristics,variation rules,and stability control of large-scale power grids with wide-area time-delay are still in the initial stage.(1)By using the network grids and equipment types,a new method based on probabilistic model is proposed for the mechanism analysis of communication time-delay distribution.In addition,a new method based on perturbation energy attenuation is proposed for time-delay mechanism analysis of disturbance propagation.The queuing theory is used to analyze the distribution characteristics of communication time-delay.Moreover,two processes is defined to describe the propagation process as traveling wave transmission on the line and generator inertia to hinder energy transmission.And then,we construct the propagation mathematical model and delay-delay mathematical expression,respectively.The simulation results demonstrate the correctness of the proposed model.(2)A compensator design scheme is proposed based on the probability distribution of communication delay.The existing adaptive delay compensator mainly determines the time-delay boundary for the random time-delay,and cannot accurately express the distribution of the random time-delay.This paper analyzes the probability distribution of communication time-delay based on the network protocol and network structure.We construct the time-delay boundary and segmentation with a certain confidence interval,and then identify the compersated time delay in the sefmentation by the probability distribution.A lead-lag compensator is designed according to the above design scheme.The performance of the compensator is verified through simulation experiments.(3)An asymptotic stability criterion and control method are proposed based on Lyapunov theory,which considers the problem of multiple time delays in large power system.The existing stability analysis only considers the fixed time-delay or the single time-varying delay.However,the type and quantity of time-delay are not unique in the power system.We establish the state equations of power system with multi-delay.Based on the Lyapunov stability analysis,this method uses the upper bound of multiple time-varying delays.A Lyapunov-Krasovskii function is proposed for multiple time-varying delays and then the asymptotically stable H? norm bound is obtained.We design a memoryless controller and feedback controller with multiple time delays,respectively.Two types of simulation models verify that the Lyapunov theory can solve the multi-delay problem in power system.(4)The Lyapunov theory brings about the computational burden especially for large scale power system A new method is proposed for stability control of power system based on the improved quadratic integral constraint.The stability theorem conbines the integral quadratic constraint(IQC)and dissipative inequality to equate the stability problem with the Kalman-Yakubovich-Popov(KYP)LMI(Linear Matrix Inequality)problem.Compared with Lyapunov method,the new method is more conservative and can solve the L2 norm bound faster since the Lyapunov function are avoied.A memoryless controller and feedback controller with multiple time delays are designed.The simulation of the large-scale power grid demonstrates the effectiveness of this method,and it is verified that the computational complexity is superior to the Lyapunov method.