Comparative Study of 31-Level Symmetrical and Asymmetrical Cascaded H-Bridge Multilevel Inverter

Multilevel inverters (MLI) are suitable for high power and medium voltage applications. Number of topologies has been introduced among which the cascaded H-bridge (CHB) inverter is widely used because of its simplicity. It consists of number of power semiconductor switches and DC voltage sources to generate step voltage waveform. The use of separate DC voltage source for each H-bridge allows the CHB inverter to be easily integrated with photovoltaic systems. Depending upon DC voltage source, the CHB inverter has two types: symmetrical CHB inverter which consists of equal DC voltage sources and asymmetrical CHB inverter with unequal DC voltage sources. Symmetrical inverter topology suffers from increased number of power devices, complexity and losses with the increase in number of output levels, whereas asymmetrical topology uses less number of power devices for producing higher level output voltage waveform. In this paper, analysis and simulation results for 31-level symmetrical and asymmetrical CHB MLI are presented.