MPPT algorithm for current balancing of partially shaded Photovoltaic modules

Among Renewable Energy Sources (RES), Photovoltaic (PV) sources represent an attractive solution because the solar energy is accessible everywhere; moreover, the price per watt of PV modules is going on decreasing. The output voltage furnished by a PV module is quite low; therefore, a series connection of different modules have to be employed in order to obtain a sufficient output dc voltage. In non-uniform irradiation conditions of a PV array, the traditional Maximum Power Point Tracking (MPPT) algorithms can converge to a relative maximum point; besides, the total power produced by the array can be lower than the sum of the maximum powers that could been produced by each module. To increase the power produced by partially shaded PV, is necessary to employ a power converter structure able to impose to each module of the PV array a different current value. The paper proposes a non-conventional MPPT algorithm able to maximize the photovoltaic energy supplied by partially shaded PV modules. To validate the algorithm, a comparison with a conventional architecture has been performed pointing out that the proposed configuration produces more power when the solar irradiation of the shaded module is greater than 20-30% of the other modules irradiation.