Investigation of Small-Scale Photovoltaic Systems for Optimum Performance under Partial Shading Conditions

Abstract

Not only are small photovoltaic (PV) systems widely used in poor countries and rural areas where the electrical loads are low but they can also be integrated into the national electricity grid to save electricity costs and reduce CO2 emissions. Partial shading (PS) is one of the phenomena that leads to a sharp decrease in the performance of PV systems. This study provides a comprehensive performance investigation of small systems (consisting of ten modules or fewer) under all possible shading patterns that result from one shading level (300 W/m2 is chosen). The most common configurations are considered for which a performance comparison is presented. Five small systems of different sizes are studied under PS. A new simplifying method is proposed to identify the distinct PS patterns under study. Consequently, the number of cases to be studied is significantly reduced from 1862 to 100 cases only. The study is conducted using the MATLAB/SimulinkÒ environment. The simulation results demonstrate the most outperformed configuration in each case of PS pattern and the amount of improvement for each configuration. The configurations include static series-parallel (SP), static total-cross-tied (TCT), dynamic switching between SP and TCT, and TCT-reconfiguration. The study provides PV systems’ owners with a set of guidelines to opt for the best configuration of their PV systems. The optimum recommended configuration is TCT reconfiguration, rather than dynamic switching between SP and TCT. The less recommended option, which enjoys simplicity but is still viable, is the static TCT. It outperforms the static SP in most cases of PS patterns.