Analysis of unbalanced system efficiency with a positive sequence power flow program

Most existing power flow programs assume balanced loading where the positive sequence impedances are sufficient to use. However, a more accurate approach is often required due to the increasing penetration of single-phase distributed generation sources on distribution grids which tend to introduce large imbalances. The proposed method uses a positive sequence power flow algorithm where the inputs are modified to accurately simulate an unbalanced system. The algorithm is tested on the IEEE 4-bus system and the results compared with published results. The impact of the analysis on system efficiency calculations are shown for the 4-bus system as well as for a large distribution system (FREEDM Green Hub) with solid-state transformers (SSTs) and distributed generation. With this modeling technique, a better understanding of an unbalanced system can be achieved and steps taken to improve the efficiency.