Global Maximum Power Point Tracking of Multiple Photovoltaic Modules under Partially Shaded Condition Using Stepped Comparison Search

For a photovoltaic system consisting of multiple photovoltaic modules under partially shaded conditions, the Power-Voltage (P-V) and Current-Voltage (I-V) characteristics will exhibit multiple local maximum power points. Under this condition it is difficult to track the global maximum power point by using conventional maximum power point tracking techniques. In this article a direct variable step size global maximum power point technique using stepped comparison search has been proposed, which can effectively track the global maximum power point when the multiple photovoltaic modules are under partially shaded conditions. The proposed global maximum power point algorithm consists of a perturb and observe maximum power point tracker, globalmaximum power point tracking and duty cycle calculation for a DC/DC boost converter, and has been implemented in a single programming module of the microcontroller. The algorithm robustness has been tested under several partial shading conditions through simulation studies. A laboratory experimental model has been used to verify the proposed global maximum power point technique.