A study on effect of blocking and bypass diodes on partial shaded PV string with compensating circuit using voltage equalizer

Abstract

When a photovoltaic (PV) string is in partial shading condition, its I-V curve has multi steps and the P-V curve has multiple maxima. Conventional MPPT (Maximum Power Point Tracking) methods could fail to track the global MPP (Maximum Power Point) in this condition. Therefore, partial shading compensating circuits which resolve this issue were proposed. In this paper, effects of blocking diodes and bypass diodes on PV strings with a partial shading compensating circuit using voltage equalizer is studied. As a partial shading compensating circuit, resonant switched-capacitor converter is chosen. P-V curves of PV string and loci of operation points were obtained by simulation with PSIM and circuit experiment. These results show that blocking diodes prevent power consumption of shaded PV modules around open circuit voltage. However, the effect of the bypass diodes were not observed.