A Robust Regularized Hybrid State Estimator for Power Systems

Abstract—Numerical instability is an inherent issue with power system state estimation, and much effort has been made to overcome this issue using numerical techniques to ensure stability. This article proposes a regularization-based method for solving ill-conditioned hybrid state-estimation problems in the presence of equality constraints. The iterative linear state-estimation problem is solved by using Tikhonov regularization. The trade-off between the residual norm and the regularized norm is controlled by the regularization parameter in the regularization method. The regularization method employs an L-curve criterion for optimal selection of the regularization parameter. At the post-estimation stage, the correction in voltage phasor at the zero-injection bus is applied using Kirchhoff's current law. The proposed method is analyzed and tested for IEEE 14- and 118-bus test systems, as well as for a 13-bus ill-conditioned system.