Dispersed generators interfaced with distribution systems: dynamic response to faults and perturbations

The installation of dispersed generators involves the critical reassessment of the adequacy of network protections, with reference to the relevant standards. The adequacy of the relay design, setting and coordination becomes critical for the proper network operation: this depends on the dynamic interaction among the various types of dispersed generators (rotating synchronous generators, microturbines, fuel-cells, photovoltaic systems) and the network. Aim of this paper is to analyse the dynamic behaviour of different kinds of distributed generators, connected to the network either directly or by means of power electronic interfaces, after the occurrence of faults and typical perturbations. Simplified dynamic models of different types of distributed generation units (microturbines, fuel cells and photovoltaic plants) are given in the paper, and the results of the simulations obtained by using realistic distribution network configurations are presented and discussed, in view of the reassessment of the adequacy and reliability of the power system protections.