Research Projects

Voltage Source Inverter (VSI)-based drives are popular in traction applications, while Current Source Inverter (CSI)-fed drives are limited to high-power, medium-voltage applications due to higher conduction losses. However, CSI has desirable features like short-circuit protection, natural voltage boosting capability, sinusoidal output voltages, and the lack of electrolytic capacitors. Recent research has shown that converter losses in CSIs can be greatly reduced using modified CSI topologies like H7-CSI, with efficiency even higher than conventional VSI configurations. This proposal explores two new drive topologies for an asymmetric dual-three-phase induction motor drive using SiC-based CSI to achieve extended speed ranges in traction applications. The first configuration uses a dual-three-phase machine fed from a VSI at one of the three-phase windings, while a three-phase CSI feeds the other three-phase winding. This topology exploits the best features of both VSI and CSI, allowing the drive to make better use of battery voltage by firing the VSI in the six-step mode. The torque ripple during six-step operation can be minimized by injecting harmonic currents from the CSI to cancel the harmonics. The second configuration uses three-phase CSIs on both windings, allowing the drive to operate with an extended constant-torque speed range even with limited or low battery voltage. This drive is also free from circulating harmonic currents and has sinusoidal voltages at all winding terminals, increasing insulation life. The efficiency and performance of both proposed configurations will be quantitatively evaluated, and appropriate field weakening algorithms will be developed as part of this research work.