Solution methods of Ill-conditioned power system state estimation: A comparative study

Power system state estimation is based on an iterative process for solving the weighted least squares (WLS) algorithm via the so-called Normal Equations (NE). This process is prone to be numerically unstable if the power system is ill-conditioned. Several reasons contribute to creating an ill-conditioned state estimator. However, this paper focuses on the effect of the high R/X ratios. A review of the main approaches that have been used for avoiding or mitigating this problem of ill-conditioning in the state estimation is presented in this paper. Additionally, simulation tests using MATLAB are implemented on 5-Bus and IEEE 30-Bus systems for evaluating these methods' performance according to their condition number and other characteristics of each process.