System Control and Reset Algorithm for Differential Power Processing Converters in a Photovoltaic Microinverter

PV-to-bus differential power processing (DPP) system can be utilized to achieve maximum power point (MPP) production for mismatched series-connected photovoltaic (PV) submodules and is examined for use in a microinverter. Series-connected PV systems can experience sudden ambient condition changes, decreasing PV power tracking efficiencies. Existing system control algorithms for bidirectional PV-to-bus converters in segmented DPP systems can achieve individual MPP tracking, but are slow to converge and cannot quickly respond to sudden changes. A reset algorithm based on PV submodule voltage sensing and PV MPP estimation is implemented for rapid PV power recovery to the proximity of the new MPP after conditions have changed and for fast convergence to the MPP during system startup. The proposed reset algorithm is tested in simulation and two different types of converter control methods are also compared. Simulation showed that MPP production was established within 0.98 seconds after system startup and PV power recovered approximately 2.6 seconds after a new set of mismatched irradiance conditions were imposed. High MPP tracking efficiency is observed in all mismatched irradiance conditions, with values up to 98.9%.