An 18-Pulse Converter and 4-Level Cascaded Inverter Based Induction Motor Drive

Abstract

This article presents a topology of an 18-pulse ac–dc and 4-level cascaded converters for a medium-voltage drive application. An isolated transformer-based 18-pulse ac–dc converter is used for enhancing the power quality at the supply end in a medium-voltage induction motor drive. Apart from this, an inverter topology, which is designed by the cascading of a two-level voltage source inverter, is designed for medium-voltage drive applications. This topology requires a smaller number of components in comparison to the hybrid four-level inverter topology, which is presented in the literature. The design of the system is carried out for an 18-pulse ac–dc converter and 4-level inverter feeding an indirect field-oriented control induction motor drive. The effect of switching and conduction losses performance of the presented inverter is analyzed and compared with the profile of the four-level inverter topology presented in the literature. A laboratory prototype of the presented 18-pulse converter and 4-level inverter is also developed to capture the performance in different operating states with a 7.5-kW (10 hp) (reduced scale) induction motor drive. The obtained results justify the practicality of this design and validate the simulated results, which are analyzed on a 298.4-kW induction motor drive. The performances of the drive system are studied based on the industry applications requirements point of view, such as power quality, losses, and dynamic stability.