Loss Analysis and Field Testing Under Various Partial Shading Conditions for Switched Capacitor-Based Cell-Level Power Balancing Utilizing Diffusion Capacitance of Photovoltaic Cells

A novel voltage equalizer utilizing diffusion capacitance of photovoltaic (PV) cells has been proposed to increase the energy yield from partially-shaded PV modules. The losses of the proposed equalizer are significantly influenced by partial shading conditions because the proposed equalizer processes the unique amount of charge depending on partial shading conditions and duty cycle. This paper investigates loss tendencies of the equalizer under various partial shading conditions. The prototype for twelve cells was built. Equalization tests under one-cell and two-cell shading conditions were performed. Although extractable maximum powers were improved by the proposed equalization under any shading conditions, losses as well as module utilization factors were significantly dependent on duty cycle. The results suggest that, to maximize the energy yield, the duty cycle of the equalizer should be properly adjusted depending on shading conditions.