New UFLS Strategy Based On Multi-partition System

Electric power can’t store in large scale, and the equipment which use to produce, transport, delivery and consume electric power have to operate synchronously, and the power system have keep the balance of power produce and consume. When the system encounters a large-scale real power disturbance, the system frequency may decrease significantly, even lead to the frequency collapse. UFLS is the last defensive line to maintain the safe operation of the system, it is one of the most important methods to keep the balance of power. UFLS shed the load based on the frequency decrease, restore the system frequency to the permitted extent as soon as possible.This paper make a theoretical analysis of power system frequency dynamic response process, proposed a new frequency analysis method which can display the time-space distribution features of frequency response process. This method divided the large system into several partitions based on simplified multi-generator system model. Then replace the partition with accurately single-generator model. The method can achieve both the accuracy of the analysis process and the little calculated amount. Using this method, an adaptive load shedding method based on multi-partitions system is designed. The concept and divide method of Power Associated Partitions; the method to determining the amount of load shedding; the method to rank the load shedding point and assign the amount of load shedding to each bus, and other issues were discussed, and gives the solution. At last, Kunder two-area system is used to test and verify theoretical analysis and load-shedding scheme presented in this paper. The simulation result show the frequency response model is accurate, and the method is effective.