Recently the number of distributed generators (DG) being integrated in to the distribution system has increased. The distribution system is no longer a single source system. Thus there has to be a change in strategy for distribution analysis. This would require a fast power flow solution with DG. This paper presents the developed three phase unbalanced power flow algorithm with the choice of modeling DG as PQ or PV node. This gives flexibility in modeling various types of DGs. The distribution system model includes modeling of lines, cables, transformers, switches, capacitors, loads and DGs. IEEE test cases are designed for testing the three phase unbalanced algorithm for single source systems. A DG was introduced in the IEEE 13-node test case and the results demonstrate the effect the DG has on voltage profile and currents. Some of the results were verified using radial distribution analysis package (RDAP)