Analysis On Factors Which Affect Frequency Dynamics In Modern Power System

Analysis of dynamic frequency process of power system is basis of system performance research,design of under frequency load-shedding scheme and evaluation of different measure of voltage regulation and frequency regulation .With development of power system, there are more and more factors that affect dynamic frequency characteristics which make it more and more complicated. The method which use single-generator-to-load model to analyse frequency dynamics can not suit for actual system. Analyzing the factors which affect frequency dynamics in modern power system is in great need.This is exactly purpose of this thesis. On the basis of discussing frequency characteristics, this thesis analyses the factors which affect dynamic frequency characteristics of simple and complicated power system separately through simulation. Main factors are pointed out. In simple power system, the factors are: active power shortage,moment of inertia,load frequency coefficient; In the loose complicated power system,the factors which make dynamic frequency dispersive are: the difference of moment of inertia,load frequency coefficient,power shortage and electric distance to hinge station of each area. The dispersion of dynamic frequency in complicated system is one of reasons which lead the unsatisfactory performance of under frequency load shedding device.The factors which affect load frequency characteristics are dissected in this thesis. Frequency characteristics of constant revolution controlled load,synchronous motor dragged load,asynchronous motor dragged load and their effect to dynamic frequency characteristics are analysed. Conclusion is reached as: increasing the efficiency of asynchronous motor can recede its slip and improve dynamic frequency characteristics.With development of modern power electronic technique, many reactive power-voltage controllers emerged which can improve voltage stability although debasing frequency dynamics at the same time. By analyzing load voltage characteristics, this thesis does some simulations of frequency dynamics of power system with or without voltage controllor and provides referenced idea of how to harmonize voltage and frequency emergency control when accident happen.