A SPWM algorithem with symetrical shoot-through states for z/quasi-z source inverters

A novel PWM algorithm with symmetrical shoot-through states for multiphase Z/quasi-Z source inverters is proposed, which is based on three carriers. Besides the basic triangle carrier, the upper carrier and the lower carrier are respectively constructed by up-shifting and down-shifting the basic carrier; then according to the size of phase modulation wave, the most appropriate carrier is selected to compare it with the modulation wave for switching signal of the phase leg. In half a switching cycle, two symmetrical shoot through intervals are distributed at the transitions from active state to null state, being in conventional null state but not at the centre, which makes the switching times reduced significantly but the output performance almost same as that of SBC PWM. The shoot through of phase leg takes place only in the biggest phase and smallest phase, so that the overlap of shoot through intervals in double carrier PWM will no longer occur in treble carrier PWM. The study demonstrates that treble carrier PWM is the modification of SBC PWM by optimizing the switching sequences, that switching times is reduced significantly, also lower ripple in inductor current and capacitor voltage is got.