Metodologia para estimação integrada de estados e parâmetros em sistemas elétricos de potência

Abstract

This dissertation presents a new methodology for state estimation (SE) in electric power systems in the presence of bad data and impedance parameter errors in transmission lines. The measurements are obtained through synchronized phasor measurement units and processed using the traditional Weighted Least Squares (WLS) algorithm. Based on this, the presence of gross measurement or parameter errors is analyzed. First, error detection is performed through a preliminary statistical evaluation of the objective function using Monte Carlo simulations. Then, error identification is carried out by inspecting the estimator’s measurement residuals. Lines whose residuals exceed the predefined system threshold are categorized as suspicious. Finally, to correct potential gross errors, the WLS algorithm is modified to accommodate an expanded state vector, which not only determines the system states (phasor voltages at all network buses) but also computes calibration factors to correct both measurements and system parameters. The calculation is performed through an optimization problem in which the calibration factors can assume different values, adjusting the measurements and parameters of the suspicious lines while respecting predefined upper and lower limits. From the problem’s solution, the states and calibration factors are determined, allowing erroneous values to be identified and corrected. Different optimization methods are employed and discussed, and tests are conducted on the IEEE 24-bus, IEEE 118-bus, and a Brazilian 107-bus test system. All case studies are compared with the traditional power flow method to validate the SE approach.