Analysis of a flexible single-phase multilevel inverter topology for photovoltaic applications

An original and an effective method for the analysis of the dc-link voltage ripple for single-phase multilevel inverters based on H-bridge and level doubling network (LDN) is given in this paper. The LDN is basically a half-bridge fed by a floating capacitor, without the need of an additional dc supply and with voltage self-balancing capability, able to increase (double) the number of output voltage levels. This configuration is particularly suitable for single-phase single-stage grid-connected photovoltaic (PV) systems, and the LDN cell can be seen also as a retrofit for existing H-bridge configurations. In order to address the design of the conversion system, with particular reference to the dc-link capacitor, PV current and voltage ripples are analytically determined and verified by experimental tests.