A Three-Level Dodecagonal Space Vector-Based Harmonic Suppression Scheme for Open-End Winding IM Drives With Single-DC Supply

Abstract

This paper presents a harmonic elimination technique based on a three-level dodecagonal space vector structure for open-end winding induction motor (IM) drives with a single-dc supply. Advantages of dodecagonal space vector switching and multilevel inverters are achieved with a single-dc supply. A dc supply-fed three-level flying capacitor (FC) inverter feeds active power to one end of the IM winding terminals and H-bridge connected capacitors eliminate fifth- and seventh-order harmonics from the other end. A pulsewidth modulation (PWM) technique is developed to switch the three-level dodecagonal space vectors and simultaneously control the H-bridge capacitors at $0.1445V_{\text{dc}}$ . The fifth- and seventh-order harmonics are eliminated for the full modulation range of the three-level FC inverter, including the extreme 6-step operation. An increase in the linear modulation range has been achieved, resulting in improved dc bus utilization. Harmonic elimination is achieved by increasing switching frequency of the low-voltage capacitor connected H-bridge inverter; thus, switching frequency for the high-voltage dc supply-fed FC inverter is not increased. Using the proposed scheme, the instantaneous phase voltage never exceeds $\frac{2}{3}V_{\text{dc}}$ (maximum phase voltage applied for hexagonal space vector structure) for which the machine windings are rated. Additionally, the proposed inverter has also been shown to operate for field oriented control of the open-end winding IM drive.