Selective Harmonic Elimination in Asymmetric Cascaded Multilevel Inverters Using a New Low-frequency Strategy for Photovoltaic Applications

Asymmetric multilevel inverters with a main and auxiliary power circuit can yield maximum number of voltage levels against the number of semiconductor devices. Most of the output power will be produced by the main inverter, which works at low frequency and the auxiliary inverters only improve the voltage quality. Advantages of the asymmetric structure are reduced number of semiconductors and gate drive circuits and better voltage quality and efficiency, which make the asymmetric inverter to be a perfect candidate for photovoltaic applications. This article presents a new switching strategy in asymmetric multilevel inverters, which exploits extra degrees of freedom to eliminate more low-order harmonics. Simulation results show this method can introduce two new switching angles without affecting the power losses of the inverter.