Study On Distributed Voltage Emergency Control Of Power System

The development tendency of modern electric industry is large-size grids connection, which makes it possible to adjust power flow among difference areas. At the same time, it could cause potential threats to the system stability. The interconnection not only makes the system dynamic characteristic more complex, but also enlarges the influence range of local fault, which makes the power system more liable to rain-failure, even collapse. Furthermore, with the popularization of electric power market and the request of environment, the power system operates close to the voltage stability limit, and the possibility of instability increases. Voltage emergency control is the major way in ensuring voltage stability and preventing collapse, which plays a very important role in the security and defense system of power system. Distributed voltage control is an important research aspect of voltage control, which meets the local essence of voltage/reactive control. This dissertation is devoted to promoting the systemic research of distributed voltage emergency control. As the chief of the dissertation, a real-time voltage control regions identification method is discussed, and then a distributed coordinated voltage control strategy based on the coordination of multi-methods used in power system urgent state is proposed, finally the hybrid model based on the improving difference Petri net of voltage emergency control is established.The dissertation firstly generalizes an overview of the history and current status of the research on power system voltage control as well as the theories and techniques of hybrid system and their applications to fields of control system and power systems. The purpose and significance of the projects is also introduced. Based on the definition of voltage emergency control and the ordinary comparison of the different voltage emergency control methods, chapter 2 proposes the ideology of distributed voltage emergency control, which identifies control region in real time and changes the control object from the pilot bus to the critical bus, i.e. the most unstable bus.In emergency state of serious contingency, the grid structure and the load status of powe system is different from the normal operating states, thereby the identification of voltage control regions should be selected according to the system status precisely. Chapter 3 presents a real-time voltage control regions identification method using the fuzzy pattern recognition to recognize the recent system operation status and selects the correspondence regions identification. It also presents a fast algorithm of the critical bus selection in this chapter. Then a distributed coordinated voltage control strategy used in power system urgent state is proposed in chapter 4, which regulates the critical bus voltage to ensure voltage stability and prevent from collapsing in two steps: first is the coordination of different reactive control methods, such as generators and FACTS units, second step is the low voltage load shedding based on self-adapting genetic algorithm.Chapter 5 gives a systemic introduction of the hybrid system theories and discusses several different hybrid modeling means, and then propose a new hybrid modeling method using the improving difference Petri net. Based on the research of chapter 5, from the point of view of control system, chapter 6 analyzes the hybrid characteristics of the distributed voltage emergency control methods from the point of control system and establishes the hybrid model of the distributed voltage emergency control in detail.At the end of this dissertation, the main results of the research are summarized. The further work is pointed out as well.