Photovoltaic systems are vulnerable to the change of climatic conditions (temperature and irradiance). They cause a declination in power generation efficiency and reliability. The variation is commonly caused by uniform and non-uniform partial shading. The aim of this paper is to present the non-uniform partial shading impact on the performances of a photovoltaic generator. Hence, a theoretical modeling of a generator composed of two series of photovoltaic panels is presented. The first part provides a literature review with a mathematical model. The second section offers details of the simulation analysis under diverse partial shading conditions.