Space Vector Modulation of a Nine-Phase Voltage Source Inverter

A generalized multi-phase space vector theory is considered for developing the space vector modulation of a nine-phase voltage source inverter (VSI). The space vector modulation (SVM) is based on the control of the voltage vector in the first d-q plane, imposing to be zero the voltage vectors in second, third, and fourth d-q planes, as in the relevant case of balanced sinusoidal load voltages. The proposed switching pattern includes one-leg commutation at a time, with the possibility to share the zero voltage between the two null vectors. The modulation limits are analytically determined. In particular, it is shown that the maximum modulation index coincides with the theoretical value obtained in the case of sinusoidal balanced waveforms of a nine-phase VSI, proving that the proposed SVM strategy allows full dc bus voltage utilization. The analysis is confirmed by a complete set of numerical simulations.