Three-dimensional space vector modulation in abc coordinates for four-leg voltage source converters

Abstract

Four-leg inverters have been selected as one of the preferred power converter topologies for applications that require a precise control of neutral current, like active filters. The main advantage of this topology lies in an extended range for the zero sequence voltages and currents. However, the addition of a fourth leg extends the space vectors from two to three dimensions, making the selection of the modulation vectors more complex. Most of the algorithms that deal with this problem require an /spl alpha//spl beta//spl gamma/ transformation. This paper presents a new space vector modulation algorithm using abc coordinates (the phase voltages) avoiding the /spl alpha//spl beta//spl gamma/ transformation. Thanks to the use of abc coordinates, the algorithm is much simpler and more intuitive than in /spl alpha//spl beta//spl gamma/ representation, drastically reducing the complexity of modulation algorithm and the computational load associated to it.