Voltage Source Inverters (VSI) are popularly used in multitudinous applications especially in motor drives and grid-connected systems. The endeavor to achieve close to sinusoidal voltage at the output of the VSIs have driven the move from standard two-level VSIs to Multi-Level Inverters (MLI). Albeit MLIs gain leverage in terms of improved voltage quality by increased number of low rating semiconductor devices used, reliability decreases with the increase in the number of levels in MLIs. Recently, three-level VSIs have been of marked interest in the industry. A number of topologies exist in literature for generation of three-level output with each topology having its own pros and cons, and the configuration is chosen based on the given application. Amongst several modulation techniques available for control of these MLIs, Pulse Width Modulation (PWM) techniques are mostly preferred due to its simplicity, especially considering increased levels in MLIs. It is also worth noting that dual-inverter fed Open End Winding Induction Machines (OEWIM) also achieves voltage states similar to that of the three-level inverters. Although different control techniques are available for motor drive applications, vector control techniques viz., Field-Oriented Control (FOC), Direct Torque Control (DTC) and Predictive Control are mostly preferred in almost all industrial applications. Recently, Maximum Torque Per Ampere (MTPA) control has gained momentum due to its inherent energy saving methodology especially in EV applications.
In this thesis, two new PWM techniques are proposed, mathematically analyzed, simulated and experimentally verified for three-level VSI fed Induction Motor (IM) drives that result in lower Total Harmonic Distortion (THD) when compared to existing PWM methods available in the literature. Besides, three more new PWMtechniques are devised and integrated into FOC of dual-inverter fed OEWIM for THD as well as torque ripple reduction. They are again validated through simulation and experimental results. Later, two modified constant switching frequency DTC techniques are designed and developed for three-level VSI-fed IM drives for reducing torque ripple especially at low speeds of operation. They are also validated with simulations and experimental results. Furthermore, two new MTPA based DTC and MTPA based predictive control schemes are designed for EV applications for not only achieving improved energy savings but also reduced ripple content in the motor torque leading to improvements in both motor and battery life.