Generalised algorithm of novel space vector modulation:: for N-level three-phase voltage source inverter

This paper concerns the development of a generalised algorithm of a novel space vector modulation (SVM) for N-level three-phase voltage source inverter. It is considering that the (N-1) DC input voltages of inverter are constant. The proposed method ensures initially the determination of the N-3 inverter switching states, the extraction of the redundancies to obtain 3N(N-1) + I independent switching states and their organisation by sector in six distinct matrices W-k with k = (1, ..., 6). After that, these matrices W-k with k = (2, ..., 6) are ordered as the matrix W-1 related to the first sector. So, the research of the three closest vectors to the reference vector is carried out only in first sector and for this purpose, the equivalent reference vector is introduced which is resulting from the rotation by -(k-1)pi/3 of the reference vector. The on-line choice of the three vectors (three switching states of the inverter) is based on the distances between the equivalent reference vector and some vectors located in its vicinity in the (alpha,beta) plane of the first sector. Moreover, a simple method for the calculation of the duty cycles for these three switching states is proposed which exploits directly the three shortest distances associated to these three selected vectors. The sequence of these three switching states over a sampling period is investigated in view to reduce the harmonic contents of the voltage output. The application is carried out on an N-level three-phase voltage source inverter, where N is an arbitrary odd integer. Finally, the phase voltage and its harmonic spectrum provided by a three-phase N-level inverter with N= (3,5,7,9,13,15) are presented to confirm the generalisation of this method. Copyright (C) 2007 John Wiley & Sons, Ltd.