Dual Inverter Configuration for Grid-Connected Photovoltaic Generation Systems

The design and control issues associated with the development of a novel three-phase grid-connected photovoltaic generation system are discussed in this paper. The scheme is based on two insulated strings of panels, each one feeding a standard two-level three-phase voltage source inverter (VSI). Inverters are connected to grid by a three-phase transformer with the open winding configuration on primary side. The resulting conversion structure performs as a multilevel power active filter, doubling the power capability of a single VSI with given current rating. An original control method has been introduced to regulate the dc-link voltages for each VSI. The proposed algorithm has been verified by numerical tests with reference to different operating conditions. The simulation results confirm the effectiveness of the whole conversion scheme.