Measurement of IEC Groups and Subgroups using Advanced Spectrum Estimation Methods

IEC standards characterize the waveform distortions in power systems with the amplitudes of harmonic and interharmonic groups and subgroups. These groups/subgroups utilise the waveform spectral components obtained by using a fixed frequency resolution DFT; while this choice represents a good compromise among different aims such as the need of good accuracy, simplification and unification. In some cases the power system waveforms are characterized by spectral components that the DFT with fixed frequency resolution can not capture with enough accuracy. This paper investigates the possibility of a group/subgroup evaluation using advanced spectrum estimation methods: the adaptive Prony, ESPRIT and root-MUSIC methods. The paper presents also the results of applications of these methods to test waveforms and to waveforms obtained from simulations of a real DC arc furnace plant