A Novel Four-Leg Inverter Topology for Dual Three-Phase PMSM

This article proposes a novel four-leg inverter topology to drive the dual three-phase permanent magnet synchronous motor (DTP-PMSM) with 180° phase shifting. Without access to the midpoint of dc bus capacitors, the proposed four-leg inverter can not only drive the DTP-PMSM with the same torque capability as the conventional six-leg inverter but also avoid the voltage fluctuations of the capacitors in the conventional four-leg inverter. Then, two kinds of pulsewidth modulation methods are given and compared for the proposed topology. The first one is the direct extension of the space vector modulation (SVM) of the four-switch inverter, denoted as SVM1, and the second one is to construct space voltage vectors utilizing almost all the switching states of the four-leg inverter, denoted as SVM2. Experimental results verify the feasibility of the proposed four-leg inverter topology and demonstrate the better harmonic performance of SVM2 compared with SVM1.