Characterization of electronic converters by time-varying harmonic phasors and waveforms

As an enabling technology, power electronics has the ability to provide effective and intelligent solutions for the grid of the future; however, the complexity and interaction with the rest of the system is non-trivial and requires careful studies. Among the issues to be addressed is the behavior of electronic converters under transient conditions. This paper investigates the behavior of electronic converters via time-frequency decomposition methods. The nonlinear electronic load is characterized by the time-varying harmonics during transient conditions such as voltage sags and variable voltage distortions. In the past, analytical expressions have been used to determine the harmonic current locus (in steady state condition) for different operating points. With the development of time-frequency decomposition tuned to the harmonic frequencies the transient performance of the harmonics can be observed with higher time resolution. This new approach enables researchers and engineers, for the first time to look into the transient behavior of harmonics and, consequently better understand the associated phenomena from a time-varying harmonic perspective. This method may become useful for determining the impact of the aggregation of multiple power electronic front-end devices. The approach may also help in setting up protection schemes based on the excursions of prominent harmonics during transient conditions.