Improved Trans-Z-Source Active-Neutral-Point-Clamped Multilevel Inverter With Continuous Input Current for Induction Motor Drives

Z-source inverters (ZSIs) are recent solutions for single-stage power conversion with boosted dc rail voltage. Trans-ZSI, employing a coupled inductor, allows high boost with lower shoot-through duty ratio. Albeit the several advantages, these converters exhibit unsatisfactory performance at low power factor due to discontinuous current conduction modes—a major concern in applications like motor drives at light loads. The objective of this article is to develop an improved Trans-ZSI with multilevel output voltage that performs well irrespective of load power factor. The proposed topology has continuous input current, low input current ripple, and the presence of active switches in the impedance network allows bidirectional current flow. Also, there is output voltage control flexibility by adjusting the coupled inductor turns ratio, shoot-through time, and modulation index. Partial shoot-through states allow nearest three vector switching for obtaining multilevel output voltage and reduced
dv/dt
. The output stage retains all the advantages of active-neutral-point-clamped (ANPC) inverter. Operating principles, analysis and a ‘simple boost control’ with carrier-based space vector pulse width modulation (CSVPWM) scheme for capacitor balancing are presented. Simulation and hardware results on three-phase, 3 HP, 220 V, 1440 rpm, V/f-controlled induction motor drives are presented to validate the proposed scheme.