MODELLING AND ESTIMATING VOLTAGE AND CURRENT HARMONICS OF VARIABLE SPEED DRIVES (VSD)

Abstract

This paper presents an analysis on the calculation of harmonic current and voltage components of a variable speed drive (VSD). The requirement for advanced and accurate harmonic mitigating techniques has become essential because of the rapid increase ofnonlinear loads like VSD’s in both industrial and commercial applications. A new state-of-the-art MATLABSimulink based harmonic calculator using DiscreteFourier Transform (DFT) was designed to calculate the current and voltage harmonics more accuratelyin order to understand the realistic extra iron loss components inside the rotating machine due to converter switching. This also helpsto optimize the system performance when a converter is coupled with the electric machine.In addition to its harmonic mitigating capabilities, this method can plot harmonic spectrum which helps to design wide spectrum active harmonic filter to eliminate pollutant odd harmonics not entering rotating electrical machines.The harmonic analysis presented in this paper is for a 5hp DC motor connected with the phase controlled rectifier. This model is suitable for virtually any application involving a VSD or similar converters to effectively mitigate voltage and current harmonics.