Minimum correction method for enforcing limits and equality constraints in state estimation based on orthogonal transformations

A new method is presented for orthogonal transformation-based power system state estimation that enables enforcement of limits and equality constraints. The enforcing of constraints is based on minimization of the correction by which the unconstrained state estimate must be modified in order to satisfy all equality and inequality constraints. An estimation algorithm is developed which combines active set and interior point optimization methods in such a way, that positive features of both methods are retained. A self-scaling Givens rotation algorithm is proposed to perform elementary orthogonal transformations in unconstrained state estimation. This reduces the necessity of the underflow monitoring and re-scaling during the orthogonal transformation of the Jacobian matrix. The numerical results are presented demonstrating the efficiency of the algorithm.