H_∞ Analysis Method For The Small Signal Stability Of Power System

Power industry is the life line of national economy, and the operation of power system with enough security and stability is one of the most important and the most indispensible guarantees towards exerting power industry's function. With the estabilshment of great projects, such as the Three Gorges Dam Project and Power Transmission from West to East, the national network interconnection will come into being. Then the problems of security and stability caused by network interconnection, espacially the problem of Small Signal Stablility, are the fatal issues, which appear in large-scale Interconnectons more and more frequently, whose harm range becomes more and more extensive in recent years, and which starves for effective solution. The thesis applys oneself to make use of the advanced Robust Control Theory to analyse the problem of small signal stability of the power system, and gives the control measure which can weaken the Low Frequency Oscillation and enhance the Small Signal Stability of the power system effectively. The main contents of the thesis are given as follows:(1) Taking the engineering background of power system into account, this thesis firstly introduces the basic conception of the H∞Control Theory and the design principle of the H∞Controller, and expatiates by the numbers on the need of applying H∞theory to the analysis of the small signal stability, and then brings forward the method of analysing the small signal stability, which is based on H∞.(2) On the basis of approximately linearizing models of multi-machine system, which are based on the system of absolute-phase-angle coordinates and the one of relative-phase-angle coordinates, the multi-machine system model, taking the exoteric disturbance into account, is given, which is used for the small signal stability analysis.(3) According to the design principle of H∞controller, Dispersed Robust Excitation Controllers in multi-machine system are designed in the thesis, and such controllers excel the existing Linear Optimal Controller obviously at the analysis guidelines, including the Damping Ratio, the General Damp and the H∞Norm of the closed-loop systems. Moreover, the given control law is network-parameter-independent, only containing local measures, and thus has strong Adaptive Capability towards the change of parameters and framework of networks, convenient for being applied in practical engineering.(4) Analyse the influence of the change of the key parameters, which are involved in the design of Dispersed Robust Excitation Controllers in multi-machine system, on those guidelines of the closed-loop system, which mainly include the damping ratio, the general damp and the H∞norm of the closed-loop system. The results have important reference meaning towards parameter distinguishing and collocation optimizing of the Robust Excitation Controllers.