| The interconnection of Distributed Generation (DG) units to a utility grid changes the configuration of traditional distribution networks. Today, DG has been one of the key driving forces in the evolution of distribution system analysis, which has been traditionally perceived as modelling small radially-connected systems with simple power flow methods. Despite its apparently simple structure, the distribution system is considerably more complex than transmission systems due to a mixture of three-phase, two-phase, and single-phase lines and transformers. This work developed more accurate modeling of unbalanced power systems to determine the impact of DG technologies on voltage regulation, taking into consideration the total system losses. The analysis was conducted with a full three-phase model because unbalanced conditions affect the behavior of the entire distribution system under high penetration of DG. A detailed mathematical formulation of line models and voltage dependency of loads was presented in order to achieve a better understanding of the distribution system characteristics. Also, a detailed description of the step voltage regulator control system was presented and related with the three-phase model of transformer banks. The IEEE 13 Node and 4 Node Test Feeders were selected to verify the validity of the proposed models. The complete simulation of the IEEE systems was carried out with the calculation program DIgSILENT. |
