Experimental Tests on a Multilevel Converter for Grid-Connected Photovoltaic Systems

A complete set of experimental tests on a novel conversion scheme for three-phase grid-connected photovoltaic (PV) generation systems is presented in this paper. The proposed scheme is based on two insulated strings of PV panels, each one feeding a standard two-level three-phase voltage source inverter (VSI). The inverters are connected to grid by a three-phase transformer with the open winding configuration on inverters side. The resulting conversion structure acts as a multilevel converter, doubting the power capability of a single VSI with given current rating. An original control method has been introduced to regulate the dc-link voltages of each VSI, allowing the whole converter to inject the PV energy into the grid and to perform as a power active filter.