Robust Control Theory Of Nonlinear Time-Delay System And Application In The Steam Turbine Generators

Since the stability of power system is paid more and more attention to in the coming connecting power system and super large connecting power system, control, which was an economical and effective means to enhance the stability of power system, became a significant and popular research branch in recent years. Control performance and robustness are the key problems to design a controller, especially in power system, which is serious nonlinear and easy changeable in structure and operating condition with time lag of information transmission. Most studies and experiences show that the proper use of nonlinear character is helpful to solve above problems. This phenomenon is also taken great consideration by many learners and gives a new approach to design a better performance controller of power system. Regarding this method, investigations below are presented in this paper.Firstly, this paper studies the stability of nonlinear time-delay systems and the problem of H_∞control. According to the orthogonal decomposition and vector field decomposition method, this paper deducts an equivalent form of the original system, and by using this form and free weighting matrix method, this paper creates a new Lyapunov-Krasovskii functional and finds the delay dependent stability. Furthermore, this paper analyzes the H_∞control of nonlinear time-delay systems, and gets a corresponding conclusion of controller design method of this system. This paper gives one simulation example to prove the validity of this result.Secondly, based on the generator control model in the single machine infinite bus system, this paper brings in time-delay and constructs mathematical model of power system with nonlinear time-delay. Using control theory brought above, this paper designs the excitation and valve controllers. These controllers not only can eliminate the effect of time delay in the system but also can perform well in the strong nonlinearity of the system. The controllers have better failure recovery characteristics and strong robustness.Finally, based on the mathematical model of single machine infinite bus system, this paper deducts the mathematical model of multi machine system, and constructs mathematical model of nonlinear time delay multi machine power system. Then this paper manages to design the excitation and valve controller, and gets the similar results with a single machine infinite bus system. In multi machine valve controller design this paper uses two different methods to design valve controller and compares their failure recovery characteristics and robustness.It should be clear that all conclusions in this paper are based on numerical simulation results.