Generalized space vector modulation schemes for cascaded multilevel inverter to reduce harmonic distortion

Abstract

Multilevel inverters are widely used in industrial power conversion newlinesystems both for utility and drives application. Multilevel inverter newlinetechnologies are receiving increased attention recently in high voltage-high newlinepower applications, due to their ability to meet the increasing demand of newlinepower rating and power quality associated with reduced harmonic distortion newlineand lower electromagnetic interference. The objective of this thesis is newlinecentered on minimizing the total harmonic distortion in the voltage output newlinewaveform. The focus of this dissertation is a cascaded multilevel inverter with newlineunequal or varying dc sources. Pulse width modulation (PWM) and space newlinevector modulation (SVM) methods are used in power inverters applied to newlineenergy conversion systems. The traditional PWM methods, sinusoidal PWM newlinemethod (SPWM) and space vector control (SVC) methods can only be newlineapplied to equal dc sources. Furthermore, complexity and computational cost newlineof traditional SVM techniques increase with the number of levels of the newlineinverter, and most of all use trigonometric functions or pre-computed tables. newlineIn addition, the existing three dimensional space vector modulation (3DSVM) newlinetechnique is applied to diode-clamped inverter and capacitor-clamped newlineinverter. Also, the 3D-SVM method cannot be applied to multilevel inverters newlinewith unequal dc sources. Accordingly, this dissertation deals with the space newlinevector modulation (SVM) of five-level inverters, especially two-dimensional newlinespace vector modulation schemes, optimized three-dimensional space vector pulse width modulation (3D-OSVPWM) schemes are proposed for multilevel newlineinverters. The two-dimensional space vector modulation can be applied to newlinemultilevel inverter with equal dc sources whereas; optimized threedimensional newlinespace vector modulation can be applied to both equal and newlineunequal dc sources. The optimized three-dimensional space vector newlinemodulation scheme has a better DC link voltage utilization and result in a low newlineharmonic distortion. newline