Design Of Excitation Control For Power System Based On Dynamic Surface Control Method

Power system is a kind of complex, nonlinear, high-order dynamic system. In recent years, with the improvement of social production as well as the higher demand of electrical energy, the capacity of a single motor is keeping increasing and the power network is also becoming more complicated now, which raises a higher demand to power system’s stability and safety. The generator excitation system is an important part of power system. It is used for controlling the voltage and distributing the reactive power of generator. Generator excitation control technology is one of the most effective and economic methods to improve the stability of power system. This dissertation discusses the dynamic surface control technology for a single-machine-infinite-bus power system in face of uncertainties and input saturation. The main contributions are as follows:Chapter one, firstly introduces the significance of stability for power system. Then a brief review of excitation control technology is given. Then the nonlinear control methods and their recent applications in this problem are introduced respectively. Finally the main work of this dissertation is summed up.In chapter two, the differential mathematical model of single-machine-infinite-bus power system with excitation control is built.In chapter three, some basic concepts of nonlinear control theory are firstly introduced. Then aiming at the nonlinear system with uncertain external disturbances, the dynamic surface control method is developed. According to the error dynamics of the closed loop DSC system, the stability of nonlinear system is analyzed.In chapter four, based on DSC method, aiming at single-machine-infinite-bus power system with uncertain external disturbances, the dynamic surface excitation control method is developed. According to the error dynamics of the closed loop excitation power system, the quadratic stability theorem for nonlinear system is deduced. And a new method of choosing and analyzing the controller parameters for DSC is presented, which makes excitation power system more stable and robust. The computer simulation shows that the algorithm is effective.In chapter five, aiming at single-machine-infinite-bus power system with input saturation and uncertain external disturbances, a new method to estimate the initial condition set which guarantees the quadratic stability for dynamic surface excitation control system is proposed. In order to reduce the conservatism of the DSC system, the estimated set is enlarged to allow some degree of input saturation. Finally, an ellipsoidal approximation of the quadratic stability region for saturation system is obtained via a linear matrix inequality approach. The computer simulation shows that the algorithm is effective.Chapter six summarizes the full dissertation and gives the outlook for future work.