Voltage stability analysis and control in power systems
Under the title of Voltage Stability Analysis and Control, three major subjects have been examined in this PhD project: the fundamental study of voltage stability, the on-line prediction method for voltage collapse, and secondary voltage control systems. The fundamental study was aimed to lay a theoretical foundation for the rest of research in this project. The on-line prediction method and secondary voltage control systems are particularly targeting on the "early prediction and prevention" strategy to tackle the rapid and "uncontrollable" nature of the voltage collapse phenomenon. The work on the fundamental study was presented in chapter 3 of this thesis. The basic characteristics of voltage collapse were examined, the theory concerning the voltage stability determining factors (VSDFs) was established. Based on this fundamental study, a knowledge based system for the on-line prediction of voltage collapse was proposed in chapter 4. The pattern recognition technique was used in this prediction system, and the design and development of such a system were intensively discussed in this chapter. As a well recognised prevention measure to voltage collapse, secondary voltage control systems were systematically investigated in chapter 5,6, and 7 of this thesis. Chapter 5 deals with the principle of secondary voltage control, and the design and analysis of such a system by classic and optimal control were presented in chapter 6 and 7 respectively. As a further study, improving voltage stability through generation dispatch was also briefly discussed at the end of this thesis. An algorithm aimed at this purpose was proposed to determine the generation participation pattern upon system load increase. All the studies in this project were simulated on the standard IEEE test power systems, some of the study results have been published in the different international conferences or academic forums.