A Study On Damping The Low Frequency Oscillation In Local Power System

This thesis investigates the relative theory of low frequency oscillation in power system and shows several ways to damping the low frequency oscillation in respect of control. By comparing the advantages and disadvantages of these schemes, this thesis presents the method of designing linear optimal controller of UPFC with state feedback. The phenomenon of low frequency oscillation is described at first and then the primary theories of it are analyzed. According to these theories we know the reason of the emergence of low frequency oscillation is lacking positive damping even appearing negative damping. This problem can be classified as dynamic stability. Afer presenting the classify and development of excitation, the way of designing power system stabilizer is proposed. In recent years, flexible ac transmission system attracts more and more people in academe and it presents a new effective method to damp the low frequency oscillation. UPFC is the focus among them. The traditional PID control theory is proposed, and then the UPFC's PI controller is designed based on UPFC's static model and its control variables. After comparing PSS,PID and linear optimal control theory, the linear optimal controller of UPFC with state feedback is proposed which is based on modern control theory. It's effect of damping the low frequency oscillation and improving the stability of power system is ideal. Finally the sub-optimal control theory is presented according to practicability. And the PSS is utilized to damp the low frequency oscillation in power system of ChongQing Three Gorges Water Conservancy and Electric Power Co. This method was proved to be effective in practice.