Optimal Bifurcation Control In Power Systems

With the development of power market and the enlargement of power systems, the optimization and coordination of system configurations from the global viewpoint has become a very important but scabrous problem.The power electric systems are typically modeled as a set of nonlinear differential algebraic equations (DAE). With combining the bifurcation theory of nonlinear systems, the optimization theory and time domain simulation (TDS) method, the optimal control of small-disturbance stability and large-disturbance stability of power electric systems are solved. Also the different control strategies of aperiodic instability and oscillatory instability are presented. The main contents of this thesis include:(1) Research on the models of power systems and ananlysis methods. The dynamic and static models of the elements of power systems, such as generators, AVRs, PSSs, loads and FACTS controllers, are presented. Then the static and dynamic bifurcations, which will happen in power systems, are introduced. A systemic method, named"Bifurcation Analysis + Time Domain Simulation, BA+TDS", is presented here to fit the research requirements of this thesis.(2) Classification of control parameters based on multiparameters bifurcation analysis. Through investigating the effects of the parameters of typical AVR and SVC controller on system bifurcations, an idea of classification of control parameters is presented. Based on this idea, the control parameters are classified into two kinds, parameters of saddle-node bifurcation control and parameters of Hopf bifurcation control. Therewith, different instability modes can select different control parameters according to bifurcation relativity.(3) The three methods of bifurcation point tracing, continuation method, direct method and optimization method, are investigated to show their differences in computing effency and solution quality. When power systems endure high pressure or suffer a contingency, its operation state may beyond bifurcation boundary and the bifurcation indices can not gain with general methods. Then a novel approach based on optimization method is presented to expand the application scope in bifurcation point tracing.(4) The definition and research status quo of small signal stability control are introduced here, showing the bottlenecks in this problem. Then, combining with the conception of small signal stability region, the small signal stability control is described as a question of optimal bifurcation control--"Assuring the uncontrollable bifurcation parametersμ≥μref, seeks for the optimal combinations of controllable parameters in small signal stability region to make the minimum control costs". Finally, the mathematic models of optimal saddle-node bifurcation control and...