Generation of multilevel SVPWM using a 3D triangular coordinate system

Abstract

The present work proposes a 3D triangular coordinate framework, triangular coordinate system, for the representation of voltage space vectors and generation of three Dimensional Space Vector PWM for multilevel inverters. In the proposed triangular 3D framework, all the three axes are oriented at 60 degree to each other unlike that used for generation of 3D SVPWM using conventional coordinate system, where the axes are at 90 degrees to each other. The entire three dimensional space divided into tetrahedral spaces whereas in the conventional 3D methods the basic unit is a cube. The paper brings out a generalised and simple algorithm for generation of 3D SVPWM for an n-level inverter. The three vectors to be switched to generate the reference vector and their corresponding durations are directly determined utilizing unique simple equations irrespective of the location of the reference voltage space vector. The algorithm also gives unique equation for direct determination of duty cycle corresponding to the three phases. The coordinate system and the generation of SVPWM utilizing the triangular coordinate system is explained for a five level inverter. The algorithm has been experimentally validated on a dSPACE DS1104 platform for a 3-level inverter and the results are also presented.