A novel multi-level inverter with low loss for 3-phase induction motor drive in electric vehicles

Abstract

This paper proposes a cost-effective 3-phase 5-level inverter scheme for induction motor (IM) drive applications in electric vehicles (EV). The proposed configuration uses up to 50% lower component count and exhibits at least 3% lower loss compared to existing multi-level schemes. This scheme works with lower switching frequency compared to commercially used two-level inverters thus exhibiting at least 10% lower switching loss, reduction in heat-sink requirement, yet yielding near sinusoid line current. The scheme restricts common mode current using isolated neutral connection, maintains continuous source current and needs no capacitor voltage balance. This scheme is configured in a way to generate a 9-level voltage with reduced harmonic content across windings of a 3-phase induction motor (IM) with stator connected in delta. A single DC supply (or power source) feeds this inverter using one isolated DC/DC converter in each phase of the 3-phase multi-level inverter with each phase having access to the DC bus midpoint without any extra diodes. This scheme exhibits lower number of isolated DC supplies compared to existing schemes. The simulated results and analysis support the effectiveness of the proposed scheme.