Islanded operation and system restoration with converter interfaced distributed generation

The current practice of distributed generation disconnection for every fault in a distribution network drastically reduces the reliability when the penetration level of distributed generators (DGs) is high. Fault isolation, islanded operation, arc extinction and system restoration after a fault are the major protection barriers which will prevent DGs from maintaining connection during a fault. In this paper, a protection scheme and an intelligent control strategy for converter interfaced DGs are proposed for a distribution network containing higher DG penetration level. The proposals can be used to maximize the DG benefits by maintaining as many DG connections as possible either in grid connected or islanded mode. The protection scheme is proposed using overcurrent relays with the aid of communication to isolate the faults in the network. The intelligent control strategy for a converter interfaced DG will enable fault detection of relays, self extinction of arc faults and automatic restoration of the network after a fault. These proposed strategies will prevent immediate DG disconnections from the network. The results are validated using MATLAB calculations and PSCAD simulations.