Electromechanical Transient Modeling And Simulation Of Power System Secondary Equipment

Modern power system is featured with extra high voltage level, long-distance and heavy power transmission, and inter-area connection. It's now operated approaching to its stability limit due to economical and environmental constraints. More and more attention is paid to power system stability and security studies nowadays.Secondary equipment plays an important role in the safe and stable operation of power system. Most reasons for the process of the accidents of power system are due to the hidden dangers which exist in the actions of secondary equipment. The operating characteristic of secondary equipment should be considered in the study of security and stability of power system, the first and foremost task of which is the appropriate establishment of secondary equipment models. The present modeling researches on power system mainly concentrate on dynamic components such as generators and loads, with no sufficient attention paid to the modeling research on secondary equipment.The main topic of this work reflects in the following areas:1) On the basis of the studies done previously the way of organically linking secondary equipment with discrete characteristic to system with continuous dynamic characteristic is well discussed.2) The modeling methods for relays and security automatic equipment are discussed from the perspective of the electromechanical transient simulation. Taking three-step distance relay and under-voltage (under-frequency) load shedding equipment for example, the mathematical models are established according to their logic of actions, the modeling method of which also adapts to researches on other secondary equipment.3) The electromechanical transient simulation program including secondary equipment is developed on the simulation program of TSSP (Transient Stability Simulation Program), using object-oriented analytical method and modularized design approach.4) The results of the simulation prove the models developed reasonable and correct well after employing standard example of transmission system, setting kinds of failure, and comparing to commercial software.