Three-phase sigma-delta modulation using zero-sequence components

This paper presents new analytic results on the performance of sigma-delta modulated (SDM) three-phase voltage source inverters, in terms of harmonic distortion of output current, conduction and switching losses of the inverter devices, and rms current of the DC link capacitor. The results are compared with the same magnitudes for PWM. For easier analysis and better visualization, a three-dimensional representation of the three-phase output voltages is chosen which also gives another view to space-vector transformation. This makes it possible to visualize the potential for optimizing SDM with respect to inverter component ratings. A zero-sequence component of the three modulator input signals is taken into account and is used to improve SDM with respect to the said performance criteria