Accurate Assessment of Harmonic and Interharmonic Currents Generated by VSI-Fed Drives Under Unbalanced Supply Voltages

Abstract

Applications of solid-state converters and inverters for adjustable speed drives (ASDs) are popular in industrial systems and lead to a significant amount of harmonic and interharmonic currents being injected into the connected system. This paper presents an accurate analytical approach for the assessment of the harmonic and interharmonic currents generated by the voltage-source inverter-fed ASDs operated under unbalanced supply voltages, where the commutaton effect of the ASD converter and the detailed motor circuit model with various load levels are included. To validate the accuracy of the proposed approach, simulation results are performed by comparing those obtained by a time-domain simulation tool and by laboratory tests. It is shown that the proposed method can effectively calculate the harmonic and interharmonic currents produced by the ASD, either under balanced or unbalanced supply-voltage conditions.