On-line tracking of changing harmonics in stressed power systems: application to Hydro-Quebec network

This paper applies to a practical test case two schemes for determining harmonics in power systems that are not limited to stationary waveforms, but can equally estimate harmonic phasors in waveforms with time-varying amplitudes and changing fundamental frequency. The first scheme relies on the short-time Fourier analysis performed using the Fast Fourier ʹIkansform (FET) with time-domain windowing and frequencydomain interpolation. Another scheme combines fundamental-frequency tracking with a Kalman filter based harmonic analyzer, yielding a uniformly sampled, self-synchronizing harmonics tracker. The performance of these advanced measurement schemes for changing harmonics is illustrated convincingly on nonstationary waveforms generated in the EMTP using a realistic series-compensated transmission network.