Development of three-phase unbalanced power flow using PV and PQ models for distributed generation and study of the impact of DG models

With the increased installations of distributed generators (DGs) within power systems, load flow analysis of distribution systems needs special models and algorithms to handle multiple sources. In this paper, the development of an unbalanced three-phase load flow algorithm that can handle multiple sources is described. This software is capable of switching the DG mode of operation from constant voltage to constant power factor. The algorithm to achieve this in the presence of multiple DGs is proposed. Shipboard power systems (SPS) have other special characteristics apart from multiple sources, which make the load flow difficult to converge. The developed software is verified for a distribution system without DG using the Radial Distribution Analysis Package (RDAP). The developed software analyzes an IEEE test case and an icebreaker ship system. System studies for the IEEE 37-node feeder without the regulator show the effect of different models and varying DG penetration related to the increase in loading. System losses and voltage deviations are compared.