A Voltage Equalizer Circuit to Reduce Partial Shading Effect in Photovoltaic String

Partial shading is one of the main causes in reducing the output power of photovoltaic (PV) systems. This paper proposes a circuit to recover the energy of shaded PV modules during partial shading condition (PSC). The proposed circuit, which is a combination of a buck–boost converter and the switched-capacitor (BBSC) circuits, equalizes the voltage of PV modules and prevents bypass diodes from bypassing the shaded modules in a string. Hence, shaded PV modules can have a contribution in output generated power instead of being bypassed. The main features of the BBSC are the utilization of the reduced number of switches in comparison with buck–boost and switched-capacitor circuits, a simple switching control strategy, and fast voltage equalization. In addition, a BBSC circuit is almost a lossless circuit during uniform shading conditions. To validate the effectiveness of the proposed BBSC circuit, both simulation results in PSCAD/EMTDC software and experimental results are presented.