Delay-dependent Stability Analysis For Power Systems Based On Wide Area Measurement System

The future development trend of the system is not only determined by the current state,but also by the past state.This type of system is called a time-delay system.In recent years,with the construction and development of power systems,it has become more and more important to conduct and study the stability analysis combining with control methods of power systems related to wide-area measurement systems（WAMS）.WAMS can use the phasor measurement unit to measure the voltage,frequency,power and generator power angle in the power system in real time,and then conduct centralized analysis and monitoring of the measurement data,which can achieve the purpose of monitoring,analyzie and control the power system.At the same time,it can provide online stability analysis of the system,and some data support for the controlling and operation of the wide-area power system.However,after the collected data passes through the WAMS,the existence of time delay between the measurement point and the control center can not be ignored,so that the power system model is transformed into a system model with time delay.In this thesis,the research on the time-delay-related stability of power systems and the main research contents are as follows:First,a time-delay power system stability criterion based on a method to determine the upper bound of quadratic function in finite interval is proposed.This criterion introduces a quadratic function and integral inequality with time-varying time-delay.At the same time,a low conservative stability criterion is obtained by constructing a new L-K functional.At last,the single-machine infinite bus system and the second-order system as example systems are used to prove that the method proposed in this thesis can achieve better results.Second,the stability of the single-machine time-delay power system based on the WAMS environment is studied.On the basis of the stability criterion of the time-varying delay power system based on the method to determine the upper bound of quadratic function in finite interval,a robust stability criterion under the condition of parameter disturbance is proposed.A single-machine infinite-bus system is modeled.The relationship between the delay upper bound,the delay rate and the disturbance is studied.Then,the relationship between the gain constant K_e of exciter and the upper bound of time delay and the gain constant K_pssof PSS is analyzed.Third,the stability of the multi-machine time-delay power system based on the WAMS environment is studied.A less conservative quadratic function upper bound determination method is used to obtain a more effective time-varying delay power system stability criterion.Then use the LMI toolbox in Matlab to get the time-delay stability margin of the proposed system.Finally,the state trajectory of the system through Simulink simulation is given,which further proves that the method in this thesis has good practical significance and superiority.