Sub-harmonic state estimation in power systems

This paper presents an approach for system-wide sub-harmonic estimation using state estimation (SE) algorithm together with the wavelet-transform (WT)-based algorithm. The WT-based algorithm is used to identify sub-harmonics in the measured power system waveforms. SE is then performed to estimate the sub-harmonic levels for the whole system based on a few selected measurements. Symbolic observability analysis (OA) method is applied to determine the system solvability for the SE algorithm from a set of measurements. Location and type of sub-harmonic sources are then determined from the estimated results. The approach is illustrated using a real power system and real field-test waveforms. The results show the accuracy of the method and its potential for analysis of noninteger harmonics