An improved Extremum-Seeking based MPPT for grid-connected PV systems with partial shading

This work deals with single-stage three-phase grid-connected Photovoltaic (PV) systems with a focus on developing an efficient Maximum Power Point Tracking (MPPT) technique under partial shading conditions. As partially shaded PV arrays exhibit a multi-modal behavior on their Power-Voltage (P-V) characteristics with a number of possible patterns, the MPPT strategy under such conditions is a complex and challenging task. An Extremum-Seeking Control (ESC) based method is proposed in this paper to track the global power peak under non-uniform irradiance conditions. It relies on the measurements of power and estimation of the power gradient to iteratively determine the segment of the P-V characteristics in which the global peak lies, without converging at the other local maxima. The proposed method is compared to the sequential ESC-based MPPT method presented in the literature. Different test scenarios of partial shading show that the proposed method can reach the global peak with a faster convergence rate and higher tracking efficiency than conventional approaches.