Investigations on harmonic spreading effects of SVPWM switching patterns in VSI fed AC drives

Abstract

Space vector pulse width modulation (SVPWM) technique has emerged as a most used modulation strategy for the voltage source inverter (VSI) fed AC motor drives. SVPWM is a method of pre-calculation of switching timing instants for various sections of target output which has options in terms of positioning vectors inside every sampling interval and has six possible patterns (variants) ofthe voltage vectors arrangements in each sector. SVPWM switching patterns, depending on the switching frequency, causes the mechanical vibration and the annoying acoustic noise to the drive system. Avoidance of the main spectral annoyance, harmonics concentration around the carrier frequency and it multiples, is done by increasing the switching frequency to a band which does not contribute mechanical vibrations and acoustic noises. This results in tremendous increase the switching losses. A systematic evaluation of SVPWM switching patterns can guide proper selection of switching frequency and vectors. A Matlab based comparative analysis of all these SVPWM variants in terms of attributes such as total harmonic distortion (THD) in output line voltage, DC bus utilization and the harmonic spread factor (HSF) is reported.