s.m. ahmed

This article discusses the operating principle and simulation of closed loop control of a three phase induction motor (IM) powered by five level diode clamped multilevel inverter (DCMLI) using direct torque control (DTC) technique. The main purpose of this article is to regulate the torque and speed of an IM and to decrease total harmonic distortion (THD). In this article, a five-level inverter's direct modulation approach with the dc link voltage self-balancing is presented. To reduce capacitor voltage variation, the redundancies of various switch topologies for the creation of intermediate voltages are also used. The use of LC filter results in lower output voltage and current distortion. A multicarrier PWM control technique is used for DCMLI to provide high quality sinusoidal output voltage with decreased harmonics. This can be obtained by employing Sinusoidal Pulse Width Modulation (SPWM) method for speed and torque control. This demonstrates that the recommended method of controlling the motor's speed and torque is effective. The simulation result reveals that DTC for the five-level inverter fed IM drive gives a rapid dynamic response, lower voltage and current THDs, and much less flux and torque distortion. The simulation is carried out in MATLAB Simulink (R2014).

Closing the supply chain loop at the end of a product’s life cycle is gaining popularity among researchers and practitioners because of its paramount influence on social and environmental issues. With the continuous adaption of the closed loop supply chain (CLSC) by developed countries, Bangladeshi automotive companies have given attention to CLSCs as a means of saving natural resources (energy, material, etc.) and reducing production costs. This paper proposed a structured framework using Delphi and fuzzy TOPSIS approaches for identifying and assessing major Bangladeshi automotive industry CLSC barriers. Through a literature review and extracting opinions from experts, a total of five major barriers and 16 sub-barriers were identified and evaluated via fuzzy TOPSIS. The result revealed that economic barriers were dominant for CLSC implementation in the existing supply chain followed by information-related barriers. This research may be a guideline to manufacturers when formulating strategic decisions and organizational visions for CLSC implementation.