A Fast Parabolic-Assumption Algorithm for Global MPPT of Photovoltaic Systems Under Partial Shading Conditions

Photovoltaic (PV) arrays exhibit multiple local maximum power points (MPPs) in their I-V and P-V characteristic curves when different modules are subjected to different radiations at the same time, known as a partial shading condition (PSC). Hence, tracking the global MPP is crucial to increase the PV system efficiency. Conventional global MPP tracking (GMPPT) algorithms suffer from slow convergence, while some can fail to track the global MPP during PSCs. This article proposes a totally new approach to finding the global MPP during PSC using a single current sensor: the parabolic assumption GMPPT algorithm uses a fixed number of current scans (steps) equal to the number of solar modules connected in series to directly and immediately calculate the global MPP. The proposed algorithm uses simple parabolic equations to calculate the global MPP near-exactly during PSCs. The performance of the proposed algorithm is first evaluated by simulation in MATLABSimulink, and then by experimental verification. The results show very fast global MPP tracking and negligible tracking energy loss with an experimental tracking efficiency over 99.6 for the four PSC patterns tested.