An Improved Three-Phase AMB Distribution System State Estimator

State estimators (SEs) are required to enable the evolving and increasingly important role of communications and control in smart distribution systems. In this context, this paper presents an improved three-phase admittance matrix-based (AMB) SE for medium voltage systems to tackle issues related to zero injections, consistency, and the inclusion of voltage measurements. Here, the state variables are the real and imaginary parts of the complex bus voltages, while power and voltage measurements are converted into equivalent currents and voltages, respectively. The key improvements include: 1) considering zero injections through a linear nonweighted procedure, 2) using phasor rotation for calculation of the equivalent voltage measurements, and 3) including the covariance between real and imaginary parts of equivalent current measurements. Despite these new characteristics, the proposed improved AMB SE (ISE) features constant coefficient matrices, thus resulting in reduced computational times. The performance of the ISE is assessed considering a real UK medium voltage system. Its consistency is assessed via a Monte Carlo analysis. Comparisons with other AMB SEs demonstrate that the proposed three-phase ISE is more robust, statistically more consistent, and computationally very competitive.