Development of Fundamental Modulation Technique Based Asymmetric Multi-Level Inverter and Multi-Pulse Converter to Prevent Medium Voltage Drive From Harmonic Component

Abstract

Low switching frequency operation is required in high-level multi–level inverter to enhance switch utilization as well as to gain excellent efficiency profile of converter with low power losses. Apart from this, variable speed drive requires voltage level and frequency variation when drive operates below base speed. Hence, a new fundamental frequency switching technique with an online angle calculation-based modulation technique is presented for a nine-level (1:1:2) asymmetric reduced switch cascaded H-bridge multi-level inverter (ARSCHB-MLI), where this technique is known as area equalization modulation strategy (AEMS). Power converters in high power range are often used, increasing power-quality issues in system. To overcome issues at drive end of system, induction motor is powered by a nine-level inverter, which is designed with a ten-switches and three-voltage DC sources per phase. For enhanced power quality performance, online angles are calculated at different values of modulation index, which changes width of steps voltage levels as speed variation of drive. This strategy ensures that quality of inverter output is acceptable as per standard regardless of drive's operating frequency. Multi-pulse converter technique is adopted at grid end to sustain power quality as per the IEEE 519 standard. This paper serves as a guideline of how one can design, operates and control of power converter for medium voltage drive system.