A Backward-Forward Sweep Algorithm for Distribution System State Estimation

Grid monitoring is today essential to provide situational awareness and to enable the smart management of distribution networks. Due to the diverse characteristics of the distribution grids, different monitoring approaches may be required, or more convenient, in each distribution system scenario. This article presents a novel state estimation (SE) solution based on the backward-forward sweep (BFS) method, which is tailored to the monitoring of radially operated distribution grids. Differently from the standard BFS algorithm used for power flow analysis, the designed algorithm allows integrating redundant measurements, including power and current measurements in the branches as well as multiple voltage measurements, as needed for SE purposes. The proposed formulation achieves the same accuracy performance of classical Weighted Least Squares estimators while offering the typical benefits of the BFS approach: simplicity, robust convergence, low computational burden, and no risk of ill-conditioning issues. This article presents the design of the BFS estimator and validates the proposed formulation via tests performed on the three-phase unbalanced IEEE 123-bus grid.