Low Complexity System for Real-time Determination of Current-Voltage Characteristic of PV Modules and Strings

This paper presents a low complexity system for characterizing Photovoltaic (PV) modules and strings in real-time, allowing accurate measurements and analysis of the actual power production of PV systems in real operation conditions. Applicability of this characterization system is in the real-time condition monitoring of such PV systems when suitable algorithms that make use of such current-voltage information (here in called I-V curve) are applied. For this purpose, a classical Boost converter is used operating as a controlled electronic load. The I-V points obtained from the load variation between the electrical terminals of the PV module or string are used to trace the whole I-V curve. The values obtained by the proposed system are compared with reference values obtained through a high accuracy I-V curve tracer available in the market, in order to validate the accuracy of the here proposed characterization system. The availability of such data makes possible to identify the presence of partial shadows that may lead to more than one local and global Maximum Power Point (MPP). It is even possible to quantify the power loss production that might raise-up due to the shadow presence, depending on Maximum Power Point Tracking (MPPT) algorithm adopted by the power converter between the PV strings and the grid or load connected to the latter one.