Switched Nonlinear Excitation Control Of Power Systems

The security and stability of the power systems is the fundamental of the people's lives and national economy. Because of the highly nonlinear characteristics of power system, linear control method is difficult to ensure power system stability under large disturbances. Furthermore, OLTC and other switching device increase the complexity of the system and the difficulty of control performance. How to effectively improve the stability of power systems by the means of advanced excitation control method is a major issue in the control theory and engineering community. This thesis investigates switched control problems of power systems via inverse system method and Hamiltonian function method. The main contributions of the thesis can be summarized as follow:First, the Hamilton realization of switched nonlinear differential algebraic systems is investigated. The dissipative of the series, parallel and feedback interconnected systems is discussed as well. Using the Hamilton functions of switching subsystems as multiple Lyapunov functions, we give some results for the stability of switched nonlinear differential algebraic systems.Second, making use of the inverse system method and Lyapunov function method, we study the excitation control problem in single machine infinite bus power system. The considered power system is feedback linearized via the inverse system method. Then we design a switched excitation controller of the partial feedback system with zero dynamics based on Lyapunov function method. Because the zero dynamics of system is considered in the feedback controller design, the proposed controller can improve the angle stability and voltage regulation requirements simultaneously.Finally, we investigate the feedback control of power system with OLTC and nonlinear loads via Hamiltonian method. We first propose a dissipative Hamiltonian realization of the power system, based on which we put forward an energy-based excitation controller. In order to show the effectiveness of the proposed controller, we construct a four-node power system with OLTC and nonlinear loads based on the Matlab Power System Toolbox. The simulation results show that the proposed nonlinear controller can effectively improve the transient angle stability and voltage stability.Because the inverse system method and Hamilton function method can effectively utilize the internal structure of the considered nonlinear system, the proposed nonlinear controllers have clearly physical meaning and are easy to complete. The results got in the dissertation have some signification in the high performance control of power systems.