SIMULATION OF EXACT MAXIMUM POWER POINT TRACKING OF PARTIALLY SHADED PV STRING USING CURRENT EQUALIZATION THEORY

Maximum power point tracking (MPPT) algorithms are among the most important research topic related to photovoltaic (PV) system. Conventio nal MPPT method give effective results and easy to perform under uniform irradiation condition. However, as more than one local maxima is formed under partial shaded conditio ns so these methods are not absolutely successful. So, output power becomes lower than the absolute maximum. Conventional MPPT is designed to track the MPP will be trapped at the local MPP. Therefore, one of the challenges is to continuously track the absolute MPP while the environmental factors such as so lar irradiation, PV temperature and partial shaded condition are rapidly changing. Also, in these partially shaded conditions, series connection of PV modules gives lowest current in PV string. Th is reduces the output power of PV string. To achieve maximum output power , a converter is connected in p arallel with each PV module provides the extra (equalization) current in parallel with the shaded module to m ake the string current equal to the maximum string curre nt. The equalization current sup ports the PV module to have its voltage regulated at a value that corresp onds to its MPP voltage. This technique is known as DMPPT (Distribute d MPPT ) method.