High efficiency of switching strategy utilizing cascaded H-bridge multilevel inverter for high-performance DTC of induction machine

This paper presents about the control switching strategies of switching frequency by using the multilevel inverter. In previous topology inverter, 2-level inverter is commonly implemented by using direct torque control technique. However, this inverter has some major problem issues which occur due to the limitation of capability the semiconductor device. Basically, there exist two problems; Firstly, high torque ripple and secondly variable switching frequency. Both problems will affect the performance in controlling the AC drive. Besides that, the 2-level inverter is not capable to operate in high power application. Over the past decades, the multilevel topology was constructed to solve the problem in high application. In general, there are three types of multilevel inverters proposed, Firstly, Cascaded H-bridge Multilevel Inverter, secondly, Flying diode multilevel inverter and lastly, Neutral-Clamped multilevel inverter. Thus, in this paper, the Cascaded H-Bridge Multilevel Inverter (CHMI) is chosen to improve the switching frequency as well as a enhance response for motor drive. An algorithm is introduced to improve the torque ripple by using information of flux status.