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Researches on Cascaded Photovoltaic Modular Systems for Performance Improvement with Power Margin Evaluation

Photovoltaic/converter modular systems offer flexibility with maximum power point tracking (MPPT) of the individual modules to decrease module mismatching losses, especially for building integrated photovoltaic (PV) systems. For achieving relatively high voltage outputs, a cascaded configuration is usually preferred at the same time. However, due to efficiency reasons, i.e. the general limit of conversion ratio, issues emerge in which not all modules can actually operate at optimal levels. This paper discusses the main issues encountered, and proposes a novel approach to evaluate power margins of PV modules at different operating levels, which can be an auxiliary criterion for judging whether some modules with lower irradiation should be bypassed or not in such cascaded configurations. Representative cases are investigated, and simulation results testify the validity of evaluating the potential and available power. The proposed approach can also be applied for practical MPPT of photovoltaic generation systems. Copyright © 2010 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.