Formulation and Performance Evaluation of a Linear Hybrid State Estimator Model Incorporating Transmission Lines, Transformers and Phase Shifters

State estimation involves computation of power system variables, voltage magnitudes and phase angles at all system buses and is one of the important functions of energy management systems. The advent of phasor measurement units has made it necessary to develop methods for state estimation combining measurements from these units as well as from older remote terminal units. Conventionally, state estimation is performed using nonlinear models challenged by initialization and slow convergence problems. This paper proposes a novel linear model that also incorporates transformer and phase shifter models. The state variables are modeled in rectangular form, with principles of circuit theory used to model the measurements. To evaluate the performance of the proposed linear state estimator relative to the conventional nonlinear estimator, simulations are performed on IEEE-14 bus, IEEE-30 Bus and IEEE-57 bus systems using MATPOWER. The proposed linear estimator provides more accurate results based on normalized cumulative error. For example, for the IEEE-57 bus system, the proposed linear state estimator gives a normalized cumulative error of 0.0043 while the conventional nonlinear state estimator gives a normalized cumulative error of 0.2202.