State estimation for unbalanced electric power distribution systems using AMI data

The distribution system state estimation (DSSE) problem is very challenging due to complexities at the distribution network structure level and sensor level. This paper first develops a DSSE formulation similar to the real world settings. In particular, unbalanced single-phase and two-phase measurements are considered. In addition, constraints associated with zero injections and center tapped transformers are carefully modeled. An orthogonal elimination based DSSE algorithm is developed to solve the nonlinear optimization problem with equality constraints. The proposed algorithm has better numerical properties than the existing methods and does not require tunable parameters. The simulation results from modified IEEE 13-bus test feeder show that the proposed DSSE formulation and algorithm yield accurate state estimation results.