The Study Of Under-frequency Under-voltage Load Shedding And Their Coordinated Approach

In order to maintain the safety and stable operation of power grid, the rational allocation of UFLS, UVLS devices and to consider the coordination problem between the two is very necessary.This paper analyzes the static, dynamic characteristics of the frequency and frequency dynamic process of the system after a major disturbance, and points out that the role of the frequency factor in the frequency dynamic changes. By appling a variety of static voltage stability indexes to find the weak integrated regional and to determine the weak link in the whole network voltage; applies the calculation method of reactive power - voltage sensitivity to determine under-voltage load shedding capacity, and develops under-voltage load shedding program in the end. Researches the coordination of under-frequency, under-voltage load shedding in some areas of larger net power, which are easy to form isolated network operation; Applies Phasor Measurement Unit (PMU) with the coordination and cooperation of under-frequency, under-voltage load shedding problem, and gives the principle.