Dual-inverter-based MPPT algorithm for grid-connected photovoltaic systems

A novel MPPT algorithm for three-phase grid-connected photovoltaic generation systems is presented in this paper. Reference is made to a conversion scheme consisting in two balanced arrays of PV modules, each one feeding a standard two-level three-phase voltage source inverter (VSI). The dc-link voltages of each VSI are regulated according with the requirement of the proposed MPPT algorithm, based on the comparison of the operating points of the two PV arrays. Inverters are connected to grid by a three-phase transformer with open-ends winding configuration on inverters side. The resulting conversion structure performs as a power active filter, doubling the power capability of a single VSI, with the additional benefit of voltage multilevel waveforms. The proposed MPPT algorithm has been successfully verified by numerical simulation and experimental tests.