Modeling of rate of change of under frequency relay for microgrid protection

This paper presents the permutation of rate of change of under frequency (ROCOUF) relay to avoid the frequency instability and voltage collapses in microgrid. When some of distributed generators (DGs) in a microgrid are disconnected from the main grid, the system may be imbalance between the power supply and the power demand, resulting in a rapid frequency decline that causes frequency instability in a microgrid. To solve this problem, this paper proposes the development of a modified conventional load shedding scheme using ROCOUF relay. The modeling and simulation of ROCOUF relay is applied and designed for inspection and identification of the severity of disturbance in a microgrid to improve the digital logic of ROCOUF relay so that preventing the frequency and voltage instability in microgrid. The simulation results in this paper are verified by using DIgSILENT PowerFactory software.