New Implementation of Common-Mode-Voltage-Eliminating Nearest-Vector-Selecting Space Vector Control for Three-Phase Multilevel Inverter

Abstract

A simpler implementation of the space vector control technique, which is selecting the vectors nearest to the reference, and whereby providing elimination of the common-mode voltage of three-phase multilevel voltage source inverters (MLVSI) is proposed. The considered algorithm applies the particular MLVSI voltage space vectors, which produce the zero value of the common-mode voltage, i.e. the voltage across the load common point and the MLVSI common point. Two normalized inverter phase voltages values (star load voltages) have been projected to the new oblique-angled 60-degree axes. These values are treated not only as the oblique-angled coordinates, but also as barycentric coordinates on triangles of three nearest zero-common-mode-voltage vectors. The offered approach helps to get rid of the drawback of the conventional implementation of the space vector control with elimination of the common-mode voltage. In particular, no multiple applying per sampling period the square function and the square root function, related to distances calculations, are needed.