A novel way for dealing with time-varying harmonic distortions: the concept of evolutionary spectra

The concept of harmonic decomposition can only be applied to steady state, periodic waveform functions. In real life however, voltage and currents are constantly changing with time. The pragmatic way of dealing with time-varying functions is to extend the time window and capture the variations along the time. However, this method can have some significant limitations and loss of physical meaning depending on the time-varying nature of the waveform analyzed. This paper suggests the application of some spectral analysis and probability distribution concepts, in an integrated way, for a better understanding of the nature of time-varying harmonics and possibly as a more precise way to treat time-varying harmonics and validate harmonic summation studies.