Hybrid State Estimator for Three-Phase Distribution Systems: An Approach Considering Technical and Economic Aspects

This paper presents a novel methodology for state estimation in distribution systems using synchrophasors and RMS (root mean square) measurements. The state variables are branch currents in rectangular coordinates and an optimization problem is formulated to determine the system state. RMS measurements are considered to be obtained from smart meters, and a phasor measurement unit (PMU) is allocated at the main substation providing the angular reference. The network is modeled considering three phase unbalanced loads, radial topology and mutual impedances. The objective function, formulated based on the weighted least squares concept, is divided into three parts, aiming to minimize the quadratic difference between estimated values and their corresponding RMS values, phasor measurements and virtual measurements associated with the null power injection buses. Load pseudomeasurements are incorporated as inequality constraints, bounded by upper and lower limits derived from previously estimated values, assuming that the estimation process is performed at regular time intervals to track daily load profiles. This research article also presents a significant contribution for both technical and economic aspects discussion, including the costs associated with the equipments for practical implementation of the monitoring system. Computational simulations are conducted using a 33-bus test feeder and a real university distribution system to demonstrate the results of the proposed method.