Study Of Intelligent Under Frequency And Under Voltage Load Shedding Modeling And Its Sensitivity Analysis

Under frequency load shedding(UFLS) and under voltage load shedding(UVLS) are the last line of defense to ensure safe and stable operation of the power system. Meanwhile, they also can maintain the power balance of power system and prevent frequency and voltage collapse of power system as an effective control method. The construction of wide area measurement system, the development of demand response technologies and the application of smart appliances under the background of smart grid provide a new direction for the development of traditional load shedding methods.This paper addresses on the UFLS/UVLS model based on smart appliances and its sensitivity analysis. Firstly, this paper analyzes the basic principles of UFLS/UVLS and their traditional tuning method. Frequency characteristics of the power system and voltage instability mechanism are carried out in-depth research. Then the performance characteristics of smart appliances are studied. This paper takes refrigerators and water heaters as research subjects, analyzes their operation mode and operating characteristics, establishes their practical model and proposes their control method on the basis of the demand side response technology. Next an intelligent under frequency and under voltage load shedding strategy is proposed and simulated in a test system. Simulation results show that this strategy can well work to suppress the frequency and voltage fall or even collapse, reduce the amount of load shedding, reduce economic losses and improve the reliability and flexibility of the power system. Finally, this paper carries the sensitivity analysis on the load shedding point and amount of load shedding, studies their impact on the frequency and voltage of power system and provides recommendations for optimizing intelligent under frequency and under voltage load shedding method.