Improvised SVPWM Strategies for an Enhanced Performance for a Four-Level Open-End Winding Induction Motor Drive

A four-level open-end winding induction motor drive (OEWIMD) is obtained when an induction motor with open windings is fed from either side with two two-level 3-Ph voltage-source inverters (VSIs) with unequal dc-link voltages, which are in the ratio of 2:1. This drive principally suffers from two problems namely: the circulation of zero sequence current in motor phases and overcharging of the lower dc-link capacitor by its counterpart with higher dc-link voltage. It has been reported earlier, that the decoupled space vector pulse width modulation (SVPWM) control strategies avoid both of these problems. This paper proposes an improvised SVPWM scheme that achieves a better harmonic performance compared to the decoupled SVPWM scheme without altering either the power circuit configuration or the voltage ratings of the devices. The proposed PWM strategy clamps the inverter with lower dc-link voltage with an active state, while the other inverter is switched around it. It has been shown that the proposed SVPWM scheme results in an overall reduction of losses for the drive system while resulting in a considerably lower dv/dtcompared to the decoupled SVPWM schemes. The four-level OEWIMD employing the proposed SVPWM scheme is simulated and is validated with experimental results.