Implementing Transformer Nodal Admittance Matrices Into Backward/Forward Sweep-Based Power Flow Analysis for Unbalanced Radial Distribution Systems

This paper proposes a new method to handle distribution transformers of various winding connections in the backward/forward sweep-based power flow analysis for unbalanced radial distribution systems. The method takes advantage of available nodal admittance matrices of distribution transformers, and can automatically solve the problem of conductively isolated subnetworks to obtain their equivalent phase-to-reference voltages. In addition, this paper presents a limitation of backward/forward sweeps, and an extension of the power summation method for distribution power flow analysis from single-phase to unbalanced three-phase. The validity and effectiveness of the proposed method can be demonstrated by numerous examples and real systems.