Implementation of a modified augmented nodal analysis based transformer model into the backward forward sweep solver

In this paper, a general method is presented to handle transformers in the backward forward sweep (BFS) based load flow analysis of unbalanced distribution systems. The proposed method is based on the modified augmented nodal analysis (MANA) approach and simply provides a single matrix that is used for both backward and forward sweep operations. The matrix is constructed in a straightforward and systematic manner, and the proposed solution technique is not restricted to a particular transformer connection and can easily handle uncommon configurations, some of which may present modeling challenges otherwise. The transformer impedances are described in full three-phase ohmic values in the matrix, which is the state of the art in distribution system analysis. Phase shifts introduced by different type of transformer connections are automatically taken into account and neutral grounding impedances are explicitly represented.