Cascaded ‘H’ Bridge based Multilevel Inverter Topologies: A Review

Multi Level Inverters (MLI) have created new revolution in industry and research in high power and medium voltage applications, also in renewable energy area. Various classical topologies of MLI are Diode Clamped MLI, Flying Capacitor MLI and Cascaded H-Bridge (CHB) MLI. The MLI requires a complex firing circuitry to fire the switches which is one of the major disadvantages of the MLI. So decreasing number of switches in MLI became main objective of researchers. Also power quality is the major factor for smooth operation of the applications. Total Harmonic Distortion (THD) of voltage wave can be decreased if the voltage wave brought to nearly sinusoidal which is possible by increasing the number of levels in the output. Among all classical topologies, CHB based inverters allows development of several new topologies because of its modular structure, more number of levels in output incorporating less number of solid state switches. In this paper, a brief review on different MLI topologies focusing overall reduction in THD is discussed.