Dynamic Modeling And Stability Analysis Of A Hydro-Turbine Governing System

The hydro-turbine and its governing system that have important effect on the stable and secure operation of the hydroelectric process are the core components of the hydropower station. In the large fluctuation transient process, the condition of the running water is complex and the parameters of the hydro-turbine governing system change violently. Therefore, people always pay close attention to the nonlinear behaviors of the hydro-turbine governing system in the large fluctuation transient process and hope to study the essential nonlinearity problem within the system to present the theory foundation of the safety and stability of the system.This graduation thesis establishes the nonlinear dynamic model of the hydro-turbine governing system in the large fluctuation transient process considering the transfer coefficients changing with the operation conditions by introducing the dynamic transfer coefficients.The main contents of this thesis can be summarized as follows:(1) We establish the transient dynamic model of the hydro-turbine governing system in the load rejection transient process by introducing the dynamic transfer coefficients. Furthermore, we use the time waveforms, bifurcation diagrams, Poincare Maps and phase orbits to analyze the nonlinear dynamical characteristics of the hydro-turbine governing system in the load rejection transient process.(2) In the process of load rejection, we analyze the stable regions of the hydro-turbine governing system and present the three-dimensional critical surface and the two-dimensional critical curve clusters of the control parameters by using the stability theory of the system. On this basis, we use the Runge-Kutta method to verify the correctness of the stability analysis by Matlab software.(3)The flow state of the hydro-turbine at a given time is determined not only by its parameters at the time, but also by its flow state in history. For the locality of the integer-order derivative, it is unable to describe the historical reliance research subjects. Therefore, we try to introduce the fractional-order derivative that has good global correlation into the large fluctuation transient process modeling of the hydro-turbine governing system. Furthermore, we study the dynamic characteristics of the hydro-turbine governing system for different orders and the results show that the nonlinear phenomena are abundant in the system.(4) In the start-up transient process, we establish the piecewise dynamic model of the hydro-turbine governing system for the two kinds of two segment linear opening rules of the guide vane and the one kind of the linear opening rule, respectively. The simulation results show that the opening speed of the guide vane has an important influence on the dynamic quality of the hydro-turbine governing system.