A NUMERICALLY STABLE DECOMPOSITION BASED POWER-SYSTEM STATE ESTIMATION ALGORITHM

This paper proposes a new approach for solving the equality constraine d power system state estimation (PSSE) problem. The proposed approach decomposes the linear least squares with the linear equality constrain ts (LSE) problem encountered at each PSSE iteration into two unconstra ined linear least squares (LS) problems. The solution of the LSE probl em is the sum of the solutions of the individual LS problems. The prop osed approach avoids giving large weights to equality constraints and hence results in a more stable formulation, that can be solved within the framework of unconstrained least squares. Based on the proposed de composition, a Givens rotations based PSSE algorithm is proposed and d eveloped It is shown that the proposed implementation is numerically m ore stable than the conventional NE, normal equations with constraints (NE/C), Givens rotations and Hachtel's methods for PSSE. The first LS problem to be solved in the proposed implementation is identical to t hat encountered in conventional constrained weighting approaches like NE approach and Givens rotations approach, except for the fact that eq uality constraints (Zero injection constraints) are not assigned large weights. The resulting error due to the lack of large weights for equ ality constraints is corrected by the solution obtained from the secon d LS problem. Simulation results on 23, 89 and 319 node systems show t he desirable stability characteristics of the proposed implementation in comparison with NE, Givens rotations, NE/C, Hachtel's approach and NE based decomposition (DNE). The proposed approach has better speed c haracteristics compared to NE/C and Hachtel's approaches. (C) 1997 Els evier Science Ltd.