A Triangular 3-D Coordinate System for Multilevel SVPWM Generation

This article presents a triangular coordinate system, a three-dimensional (3-D) coordinate system in which the three axes are oriented at 60 degrees to each other. The 3-D representation of multilevel inverter voltage space vectors and generation of 3-D space vector pulsewidth modulation (3DSVPWM) using this coordinate system is proposed. The proposed 3DSVPWM method offers advantage of simplicity, amenable for implementation in field programmable gate arrays (FPGA) and application specific integrated circuits (ASICs), and flexibility for common-mode voltage control. The existing methods for 3DSVPWM generation operate on a 3-D space, with the axes oriented at 90 degrees. The conventional 3DSVPWM methods require switching among four vectors, located at vertices of a tetrahedron, in a PWM cycle. In addition, the triangular coordinate system offers flexibility to directly extend any two-dimensional SVPWM (2DSVPWM) algorithm to 3-D, since it also involves switching of three vectors located at vertices of a triangle. The proposed method of 3DSVPWM generation is generalized and can be extended to any n-level inverter. The three vectors switched to approximate the reference vector and their corresponding durations are directly determined utilizing arithmetic operations. The coordinate system and the generation of SVPWM utilizing the triangular coordinate system is explained and experimentally validated on a dSPACE DS1104 platform for a five-level open-end winding inverter configuration and results are presented.