A 40-Pulse Multiphase Staggering Modular Transformer With Power Quality Improvement in Multilevel Inverter Fed Medium-Voltage Induction Motor Drives

In this article, a new configuration of the adjustable speed drive is proposed for the medium-voltage industrial induction motor drives (IMDs). Here, a new configuration of a 40-pulse multiphase staggering modular transformer is proposed for power quality improvement in the vector-controlled induction motor drive (VCIMD) at the utility end. In it the two transformers (T-1 and T-2) are utilized and both have extended-delta configured input windings with +9 degrees and -9 degrees phase shift and their secondaries have two sets of five-phase ac supplies to achieve a 20-pulse ac-dc conversion. Because of these primary angles, these two transformers are reconfigured as a 40-pulse ac-dc converter. A new cascaded multilevel inverter (C-MLI) is proposed at the drive end. This C-MLI is cascading four two-level voltage source inverters in a unique manner to get nine levels in its line voltage. A modified sinusoidal pulsewidth modulation strategy is utilized, which offers very low switching frequency, low switching losses, enhanced fundamental magnitude, and low total harmonic distortion. The performance of the proposed VCIMD, is evaluated by simulating it in MATLAB Simulink. The performance of the proposed VCIMD is also verified using a scaled down laboratory prototype under various operating conditions such as steady state, starting, load perturbation, speed control, varying load conditions, and over a wide speed range of IMD.