Performance Comparison of Asymmetric Seven Level Inverter for Solar Photovoltaic Systems

This paper presents a comparative study on performance of asymmetric seven-level inverters. This study has been carried out with four topologies of asymmetric multilevel inverters: (a) packed U cell type, (b) asymmetric cascaded H-bridge type, (c) multi-string type, and (d) asymmetric reduced switch type. A trapezoidal alternative phase opposition disposition pulse width modulation scheme is considered for generating firing pulses of switching devices. The comparison is done based on a number of components, inverter losses, total blocking voltage, and the quality of output voltage waveform. The comparative results of this study suggest, the packed U cell and multi-string seven-level inverters use the lowest number of components which is around 20% less than the asymmetric cascaded H-bridge and the asymmetric reduced switch topologies. They also provide low total blocking voltage than other topologies. The lowest inverter loss is found in asymmetric reduced switch topology which is around 7.69% and 24.92% lower than packed H-bridge and asymmetric cascaded H-bridge topology respectively. The whole work is carried out with MATLAB/Simulink environment.