MPPT for Photovoltaic Array under Partially Shaded Conditions

Power characteristics of photovoltaic systems can have multiple peaks when under partially shaded conditions. This can cause traditional power tracking methods to operate at the lower power peaks. This research looks at two alternative power tracking method designed for partially shaded conditions. Random Perturbation search method was one of the algorithms investigated. The method is based on perturbations of random but limited magnitude. Even Perturbation search method was the second algorithm investigated. The algorithm scans through the appropriate range of operation with constant size perturbations. Both methods operate on periodic bases for considerations of power loss. Through experiments both search methods have demonstrated good accuracy and consistency with uniform irradiation and for most cases of partial shading. The search methods were combined with the 'Perturb and Observe' algorithm to improve the response speed to irradiance changes. Both of the improved methods showed significant improvement in response speed and results were consistently accurate. Overall, the developed maximum power tracking methods have met the design goals.