Studies On Excitation System In Transient Stability Analysis

The interconnection of wide-area power systems in our country has emerged in its embryonic form. We, however, have encountered a lot of problems in the process of guaranteeing the sound and economical functioning of it, among which how to get informed of the circulation of the power system speedily and truly and give critical and valid guidance accordingly are the most important and urgent one. As a result, the development of real-time simulation software for large scale power system becomes increasingly pressing. The characteristics of the power system suggest that a correct model to simulate the circulation of the power system is needed.In the regulations for power system's stability and security established by the State Grid corporation in 2006, the standard models of excitation system, which were used to analyze system dynamics. The main contribution of this dissertation is how to realize those models in transient stability analysis.This paper firstly summarizes the development of excitation system, working principle and function in the operation of power system. Then the function and mathematical model of each unit of the excitation system are introduced in detail. Alternative evaluation method and simultaneous solution method, which are the two main methods to solve simultaneous equations in Numerical Integral Algorithm for transient analysis, were analyzed and compared. Then the bi-directional iteration algorithm which integrates advantages of the previous two approaches is introduced hereafter. How to obtain the difference equation and initial value of state variables is an important step in the transient analysis. Direct current excitation system, alternating current excitation system and static excitation system are deduced as examples to explain the importance of this very step. At last, the realization of evaluation system is studied in the IEEE 4-machine 11-bus test system. The simulation results can well approximate to that of BPA. The validity of the proposed approach is verified.