A mixed pivoting approach to the factorization of indefinite matrices in power system state estimation

A robust and efficient sparsity oriented approach to the factorization of indefinite matrices that appear in connection with a variety of power system state estimation formulations is presented. Particularly, the problem of representing zero injections as equality constraints in the normal equation formulation is discussed and analyzed. A new ordering scheme for mixed 1*1, 2*2 pivoting is proposed and tested. Tests on two real life systems (41 buses and 1331 buses) are reported and discussed.>