State estimation for distribution systems with zero-injection constraints

In this paper, a new fast decoupled state estimator with equality constraints is proposed for three-phase distribution systems. Lagrange multipliers were utilized to deal with the zero injections. The proposed method is based on equivalent current measurement and rectangular coordinates. The method uses a compact constant-symmetric gain matrix which can be decoupled into two "identical" sub-gain matrices. The update and factorization of the gain matrix needs to be done only once. Tests have shown that the proposed low-storage method is efficient, accurate and robust in solving the state estimation of unbalanced three-phase distribution systems.