Substring-MPPT for 4-Terminal 3-Substring Modules

35th European Photovoltaic Solar Energy Conference and Exhibition; 1393-1395
State of the art residential photovoltaic (PV) systems are sensitive to partial shading. Shaded modules subjected to lower solar irradiance result in lower current in a PV-string. To minimize power losses string inverters activate bypass diodes in a shaded module resulting in unused power potential. Common module-based power optimizers (MPO) or module inverters lead to mismatch losses in shaded PV-modules. Individual substring maximum power point tracking minimizes mismatch and shading losses for a partially shaded module, resulting in a higher shaded module power output compared to MPOs and bypass diodes. A first unoptimized Substring-MPPT prototype adapted to one substring shaded by 25 % and another one shaded by 30 % raises the output power from 34 % of the theoretical maximum to 90 % whilst avoiding hotspot generation.