Adaptive FOCV-based Control Scheme to improve the MPP Tracking Performance: an experimental validation

Nowadays the photovoltaic (PV) is one of the most renewable source device used in the harvesting system to support the life time of stand alone devices like sensor node. One of the most diffused method to increase the PV efficiency is the Fractional Open-Circuit Voltage (FOCV) that allows the PV to work around its estimated Maximum Power Point (MPP). To increase the solar harvesting system efficiency both static (in terms of efficiency) and dynamic (in terms of MPP tracking responsiveness) performances are of crucial interest. Most of works in the literature focus on improving the static system performance by giving a more accurate MPP estimation. In this paper, it is proposed a FOCV-based algorithm to improve system dynamic performance in terms of MPP tracking performance and energy conveyed to the load under varying solar irradiance conditions. The MPP system dynamically adapts the MPP estimation to the solar irradiance condition by mean of a ”smart timer” circuitry that continuously adjusts the operative frequency of the sample and hold component. A detailed hardware implementation description of a smart timer as well as a related analytical analysis used for component design are presented. An experimental validation and a comparison of the proposed approach than the standard FOCV based method are carried out. The results show the effectiveness of the proposed scheme in improving dynamic system performance in terms of tracking performance and timeless to convey solar energy to the load storage component (i.e. ultracapacitor).