Stability Analysis Of Multi-machine Power System And Nonlinear Controller Design

Modern power system is a hierarchical distribution of dynamic systems with strongly nonlinear and high-dimensional.Along with the rapid development of the power industry and constructed in human history,it has become one of the most complex industrial system.But more and more close to stable operation of its stable limit and therefore power system security problems are becoming more acute.How to exert a measure of control of power systems to improve and increase the stability issue has become a pressing task for experts and scholars.In view of this,the paper focuses on controller design problem of the third order power system model by using the backstepping,minimax,and immersion and invariance method,in order to improve the transient stability of power system performance.In particular summary is as follows:(1)Firstly,A brief review of power systems on the main control objects and the basic control problems is gave.Then we introduce the stability of power systems and its new results respectively.After that,the nonlinear control methods and their recent applications in power systems are introduced.Finally,the main work of this dissertation is sum up.(2)The excitation control problem in multi-machine power systems is discussed.Considering that the system may get large-disturbance suddenly from the generator which has occurred mechanical power disturbance,a controller of nonlinear large-disturbance rejection is designed by using backstepping method combined with minimax method;The steam valve control problem in multi-machine power systems is dealt with.A design methodology of nonlinear large-disturbance adaptive control about minmax is proposed by using backstepping combined with Lyapunov method.Considering the case that the boundary of uncertain parameter is known,the nonlinear minimax controller and the parameter adaptive law are designed to make sure that the steam valve system is insensitive to large-disturbance,and the interference processing conservative is reduced effectively.(3)In this paper,to aim at Reheat-type valve control of steam turbine generator set,based on the deterministic equivalent thought,I advance a nonlinear adaptive interference suppression control recursive design scheme.In the process,I design the parameter estimation error primarily using the method of minimax advantage to discuss the system disturbance occurs,the biggest impact on the system damage,considered the controller designed by this method ensures the ensure that the system has good robustness and is not sensitive to large disturbance.At the same time I introduce k-class function in the discussion of system controller design and considering the transient response and controller,in order to improve the transient stability performance of the system.(4)Transient stability problem for multi-machine infinite bus system with the generator excitation was addressed via the non-certainty equivalent nonlinear re-parameterization method.The system need not to be linearized.The damping coefficient uncertainty was considered.A non-certainty equivalent excitation controller and a novel parameter updating law were obtained simultaneously via adaptive backstepping and Lyapunov methods to achieve stability of the error systems.(5)We propose a nonlinear state-feedback controller design scheme based on immersion and invariance methodology for single machine infinite bus systems with TCSC.A nonlinear damping controller is obtained by choosing a stable target system and some designed mappings,which efficiently avoids choosing Lyapunov function and guarantees that all trajectories of the closed-loop system are asymptotically stable and bounded.Concluding remarks are presented at the end of this dissertation.Some interesting problems are also pointed out,which deserve further study.