the output power quality, device voltage sharing, power converter flying capacitor voltage ripple and motor torque ripple at low-frequency/ speed operation are the major issues in high-power medium-voltage (mv) motor drives. in this thesis, a new four-level multilevel converter (4l-mlc) is proposed for mv drive applications. the proposed converter does not require series connection of devices, thereby the voltage sharing problems will be eliminated. also, the new mlc does not require any isolated direct current (dc) sources and eliminates the need of complex phase-shifting transformer. furthermore, the proposed mlc is also suitable for back-to-back operation due to the presence of a common dc-link. [...]