Medium Voltage Induction Motor Drive feed by Multi Pulse Converter and Asymmetric Multi Level Inverter with On-Line Angle Selection based Modulation

Abstract

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