A Novel Topology Of Pwm Modulation Technique For A Cascaded Inverter With An Induction Machine

This paper proposes a cascaded H-Bridge Multilevel inverter for induction motor drives (CHMLI). Multi-level Inverter (MLI) has several advantages over conventional inverter such as lower total harmonic distortion (THD), low switching loss, good power quality, high output voltage. The main feature of multilevel inverter is that it uses many small dc sources to supply various output levels. The H-bridge cascaded MLI is chosen in this paper because it requires least number of components for same voltage level. The H-bridge cascaded MLI with five levels is designed. The simple multi carrier SPWM techniques namely phase disposition (PD) or phase opposition disposition (POD) is usually used to generate pulses for the MLI.In this paper, a new topology of Multi Carrier PWM techniques known as Hybrid Trapezoidal Carrier PWM Technique (HTrap) is used to control switching of multilevel inverters with a squirrel cage induction motor drive.The H-bridge cascaded MLI with five levels using HTrap modulation technique is simulated and synthesized for induction motor drives. The performance of designed CHMLI fed induction motor drives is investigated extensively for various operating conditions through SIMPLORER simulation. The performance of CHMLI with HTrap modulation technique is also compared with other conventional multicarrier techniques in terms of inverter performance parameters (total harmonic distortion, THD, harmonic factor, HF and crest factor, KF). The promising and interesting results obtained are comprehensively presented.The five-level multilevel inverters with HTrap showed to have the lowest THD, HF and KF when filters are not used as compared to other Multicarrier PWM Techniques. If the cost is important the two-level inverter should be used, since it has the lowest cost between all of the inverter topologies. If the power losses are important, the five-level is the best choice since it has the lowest power losses than the two level inverter. Selection of a multilevel inverter is a tradeoff between cost, complexity, losses and THD. The most important part is to decide which one is more important.