Research On Power System Dynamic Frequency Stability And Control Technology Considering Time Delay

In load frequency control(LFC)of power system,the feedback signal needs to realize a large number and wide range of information exchang e with the help of communication network.The time delay encountered in the transmission process worsens the system performance and reduces the stability performance,which is not conducive to the safe and stable operation of large-scale interconnected system.Therefore,in order to improve the operation reliability of interconnected system,considering the time-delay link in the stability analysis and controller design of power system plays an important role in improving the safe and stable operation of the system.The main research work of this paper is as follows:(1)By analyzing the basic principle of LFC and network time delay characteristics,a discrete state space model of LFC considering time-varying time delay characteristics is established,the influence of network transmission time delay and controller parameter changes on system stability is studied,and it is revealed that system parameter changes affect the system stability.The influence law of dynamic frequency provides a theoretical basis for the parameter design of the controller.(2)Aiming at the time-delay problem caused by communication channel in load frequency control,the Lyapunov-Krasovskii functional is constructed by introducing cross term,augmented variable and cubic summation term.The upper bound of Lyapunov function difference is estimated by using multi summation inequality technology.A Lyapunov stability criterion for discrete time-delay systems with low conservatism is proposed to solve the stability margin of interval time-varying delay LFC systems.On this basis,the nonlinear term is treated by variable substitution method,and then the output feedback criterion is derived to realize the controller parameter design considering time-varying delay.The simulation results show that the designed controller can effectively suppress the frequency oscillation of the system under small disturbance and make the system have time-delay stability.(3)In order to reduce the communication burden between regional power grids and comprehensively consider the joint effects of event triggering conditions,controller gain and communication delay,a controller collaborative design scheme based on event triggering and output feedback control is prop osed to ensure the frequency stability of power system and improve the efficiency of data tr ansmission.Through the example analysis,it is verified that the proposed controller can effectively suppress the system frequency and tie line power oscillation a nd reduce the oscillation times under the condition of time delay,so as to ensure good cont rol performance.At the same time,it significantly reduces the traffic of network transmission and reduces the network burden.