Direct Hill Optimization for the Efficiency Maximizing Flexible Power Point Tracking of a PV Array under Partial Shading

The flexible power point tracking (FPPT) is the recent trend to control the power output of the photovoltaic (PV) array as per a user specified power reference command. As the power reference line may intersect a multi-modal power-voltage curve at two or more operating points, the FPPT control under partial shading has to face an additional challenge of finding out the best operating point apart from avoiding the local peak blockage. The operating point at the highest voltage level is preferable as it reduces the thermal stress on the array converter by maximizing its power conversion efficiency. An efficiency-maximizing FPPT based upon a metaheuristic optimization algorithm was already proposed in the literature. However, as a metaheuristically implemented power tracking procedure leads to vigorous power oscillations. A direct hill optimization procedure to assist the conventional sweeping-based FPPT is proposed in this paper. The proposed direct hill optimization is similar to the global maximum power point search procedure, but is aimed at finding the hill that contains the most energy-efficient reference-line power point. Simulation results are produced to demonstrate the power tracking time improvement because of the direct hill optimization Instead of a metaheuristic power tracking.