Stability Analysis And Control Of Power System With Time-Delays And Uncertain Parameters

In nature,the future development trend of the system is not only dependent on the current state,but also related to the past state.This kind of phenomenon is called time delay.Therefore,the system with time-delay is called time-delay system.At present,a large number of scholars have carried out in-depth research on time-delay systems,and formed a series of theoretical results.With the in-depth reform and development of the market economy,the power grid of our country towards large-scale development.The expansion of scale means that a huge communication network is needed as the support.In the process of information transmission,it is inevitable that there will be time delays,which will affect the stability of the power system.In addition,the mathematical model established for the actual power system can not be100% accurate,and the slight change of load,and the change of high-altitude cable reactance,which inevitably lead to the system parameter disturbance.Therefore,in this paper,the theoretical results of time-delay system are applied to the actual power system,focusing on the stability of time-delay and design of robust stabilization controller for power system with parameter disturbance.The main research results are as follows:(1)Based on the integral inequality method,the stability of power system with constant time delay is analyzed.This paper not only considers the disturbance of system parameters,but also considers the multiple time delays.By using the new integral inequality to deal with the integral term of Lyapunov functional derivative,the stability criterion of the constant time-delay power systems with multiple time delays is derived.The delay stability margin of the typical second-order time-delay system,the single machine infinite bus power system and the double time-delay second-order system is calculated by LMI toolbox,and it is proved that the method is less conservative and practical.(2)Based on Bessel Legendre inequality,the time-delay dependent stability of power systems with PID control parameters is analyzed.In this paper,an augmented Lyapunov functional is proposed,and Bessel Legendre inequality method is used to analyze the stability of single area power system based on PID control in the case of small disturbance parameters.The influence of different control gain parameters and system parameter disturbances on power system stability margin is analyzed by using the proposed method.(3)Based on the method of parameter adjustment,robust controllers for time-varying time-delay power system is designed.Based on the constant time-delay power system model,the uncertain time-delay power system model is established.By using Bessel Legendre inequality method to deal with the integral term in the derivative ofLyapunov functional,a delay stability criterion with less conservativeness is obtained.According to the obtained stability criteria,the memoryless feedback controller and the feedback controller with memory are designed by LMI technology.The stabilization of the controllers is verified by the analysis of the typical second-order delay system and the single machine infinite bus system.