1. IntroductionShading is the most important cause of vulnerability for PV module power output. 5% (for example) of shading on the PV module results in a reduction in the capacity of the module which can reach more than 60 or 70% of the module power. This is due to cells connected in a chain, where the cell with the lowest illumination is the main reason for the current series to completely collapse. On the other hand, it is possible that the cells become reverse biased and that power dissipation by the rest of the cells in the chain creates "hot spots" that have the thermal potential to destroy the module. This is why all causes of shading should be avoided on PV modules. Shading due to buildings, chimneys, trees, towers, or even other parts of the same building.2. Research2. 1. Previous ResearchShading, which is located on one cell of a group of cells connected in series, leads to the reverse bias in these cells, the reverse bias and degradation of microplasma was explained and described physically by Bishop (1988) . a comprehensive analysis was carried out on reverse polarization solar cells and applied to the Bishop model by Kovach (1995), in order to obtain conclusions regarding the formation of hot spots and the reduction in efficiency of photovoltaic panels. Alonso and Chenlo (1988) gave measurements for crystal cells and amorphous cells which led to commercial availability. Kovach (1995) again found that poor arrangement of photovoltaic panels and under the same shading conditions lead to significant energy losses, and that even small shadows can significantly affect energy return. The researchers also observed that all characteristics of UI solar cells in reverse bias show more variation with respect to the bias...... middle of article ...... electrical behavior of shaded photovoltaic panels. First, Rauschenbach (1968) presented a mathematical description of shaded photovoltaic panels. After that, Abete et al. (1989) studied the behavior of solar cells connected in series and in parallel, subjected to partial shade by applying the Bishop model. Today, the commercial market thrives on a huge number of software tools capable of evaluating the behavior of photovoltaic panels. But not all test the level of solar cells under reverse bias conditions (Zehner, 2001). RESEARCH QUESTIONS: - How to estimate the reduction in energy yield of partially shaded photovoltaic systems? - How to make changes in the system design to bring about improvements in power generation efficiency? - What are the latest methods that can be adopted to overcome the disadvantages associated with shading? - What are the advantages using a microinverter ?