Relay coordination in microgrid

Microgrids has many environmental and economic benefits but their implementation has great technical challenges in protection, energy management and control. MG consist of a number of distributed generators (DGs). Distribution system protection is the most important technical aspects in the microgrid. Distributed Generation (DG) is used to supply the local loads. The insertion of distributed generation in the microgrid leads to violating the relay coordination in the distribution system. The continuous connection and disconnection of DG affects coordination of distribution system protection, as the generator has the ability to contribute large fault currents to the fault point which causes changes in magnitudes and directions of short circuit currents that leads to false trip or fail to trip over-current protection relays in the system and thus inaccurate operation of the existing protection system. Thus, coordination between the primary and the backup relays fails and has an adverse impact on protection coordination. The adaptive protection algorithm is used for optimum operating time and coordination between the primary and the backup relay and an optimal DG placement to maximize the penetration level of DG in distribution networks without changing the original relay protection schemes. Based on the impact analysis of the number of DGs, their locations and capacities upon short circuit currents, different levels of faults conditions are seen in this paper. Genetic Algorithm (GA) is used for optimization of the objective function in the distribution systems. Simulation is done in ETAP software on a standardized IEEE 9 bus system to obtain load flow and short circuit analysis.