Reduction of Total Harmonic Distortion Using Filtered SVPWM in Multiphase Voltage Source Inverters

In recent years, multiphase PWMs have been proposed because of their increased efficiency, reduced torque pulsation, improved fault tolerance, and lower power handling requirement by adopting multiphase machines. In the digital implementation, multiphase reference voltages are sampled and fed into the digital modulator to produce gating signals at a constant clock rate f. This means a finite pulse-width resolution because the gating state transition can only occur at some specific time instants depending on f. This will result in a deviation of produced phase voltages from the desired phase voltages, i.e., increasing harmonic distortion especially for a small modulation index signal. In the present paper a filtered space-vector pulse-width modulation (SVPWM) considering finite width resolution is proposed to produce a switching sequence with reduced baseband harmonics for multiphase voltage source inverters (VSI). This is achieved by incorporating a pseudo feedback loop regarding weighted voltage difference between desired and produced phase voltages.