An enhanced global MPPT method to mitigate overheating in PV systems under partial shading conditions

The hot-spot phenomenon in photovoltaic modules is a reliability issue typically caused by many reasons, including partial shading conditions. In such situations, the P-V curve exhibits a unique global maximum power peak (GMPP) and several local maximum power peaks (LMPPs). However, all the existing tracking methods (GMPPT) track the GMPP, even for a slight difference between peaks. For this purpose, an experimental investigation of the relationship between the operating point of a PV module and the temperature of their shaded parts has been carried out. In the studied case, it was found that the shaded cells’ temperature exceeds 99 °C, and it is directly related to the GMPP position on the P-V curve, where it decreased as the operating point is moved from the short circuit current towards the open-circuit voltage. As the shaded cells' temperature may reach high levels, which can result in early degradation of PV modules, an enhanced GMPPT method is proposed in this paper to handle the overheating issue. The proposed method aims to track the secure peak when two peaks or more have closer power values. Consequently, it alleviates the overheating and hot-spotting risks. Furthermore, the scanning voltage interval of this technique is bounded by lower and upper voltage limits. The proposed technique is experimentally validated and compared to two existing methods: the 0.8 Voc and the full sweeping method. The results show that when the power peaks have approximately the same value, the proposed method tracks the peak with the upper voltage (automatically the lower current) to minimize the thermal stress within the shaded cells. Moreover, the proposed method exhibits a 40 % saving in tracking time compared to the full sweeping method thanks to the efficient tracking mechanism that allows skipping certain intervals in the search space.