Power flow analysis for interconnected T&D networks with meshed topology

This paper proposes an extension for the conventional power flow formulation in order to enable it to process interconnected transmission and distribution (T&D) networks with meshed topologies. The proposed extension applies a complex per unit normalization to adequate X/R ratios of Distribution Feeders (DF) to the same levels of Transmission Systems (TS). Additionally, active and reactive power compensations are included at each T&D boundary bus and treated as new state variables, so that the power flow solution of the normalized system is the same as in the original network. Appropriate equivalence between power flows through branches connected to boundary buses are included as new equations, resulting in a solvable non-redundant set of algebraic equations. The impact of these modifications on the power flow solution via Newton-Raphson´s method is also discussed. The proposed approach provides an efficient tool to perform power flow analysis on T&D systems, where DFs are explicitly represented, allowing an accurate determination of their impact onto the transmission operation. In addition, meshed topologies can be easily handled by means of the proposed approach, and simulation results conducted on an illustrative test-system are shown in the paper. Distinct operational conditions between T&D parts of the test-system allow both the evaluation of the features and the performance of the proposed approach.