Low Cost, Stand-Alone, In-situ PV Curve Trace

The i-v characteristic curve provides information about the parameters and operation of a photovoltaic (PV) module to validate its performance and efficiency. A flexible and scalable i-v curve tracer was developed to measure this experimentally. It consisted of a source measuring unit (SMU), a relay board, and a computer hosting MATLAB running a custom script to control the curve-tracer setup. However, the system is expensive for many institutions, such as developing countries, where researchers may lack resources and funding. Therefore, this paper describes an improvement to reduce the cost by replacing the computer with a $35 Raspberry Pi and the MATLAB script with a free Python program. The SMU and the relay board are connected to the Raspberry Pi through a USB cable and an ethernet cable, respectively. The new software provides four modes of operation called F1, F2, F3, and F4. The first mode is the one-time test mode (F1), in which the user tests one or multiple PV modules. In addition to generating individual plots, the software generates a composite figure of all the selected PV module curves, useful for comparative studies. The second mode, F2, runs a time-sequenced test of F1, in which users test a set of PV modules for a specific duration in regular intervals. The next mode (F3) enables different testing interconnections by configuring relays based on the connections described in an excel file. The final mode, F4, is a time-sequenced version of F3, by which users can test all the configurations in excel for a specific duration at regular intervals.