Maximum Power Extraction From a Partially Shaded PV Array Using Shunt-Series Compensation

Under partially shaded conditions, the current through a photovoltaic (PV) string is limited to the current produced by its most shaded module, reducing the overall PV array output power. A current compensation-based distributed maximum power point tracking (DMPPT) scheme may typically be used to maximize power output under these conditions. However, because of nonuniform irradiation during partial shading, different modules across a given string, as well as across the various strings, experience different conditions. Yet, the module voltages in all the strings should add up to the same voltage because all strings are connected in parallel. This causes the individual modules in a string to readjust their voltages and operate away from their actual MPP. In other words, the DMPPT scheme using shunt current compensation alone is not effective. This paper describes a novel method comprising shunt (current) and series (voltage) compensation of modules and strings, respectively. Per this technique, a current-compensating converter is connected in shunt with each module, and a voltage-compensating converter is connected in series with each string. This facilitates each PV module to operate at its exact MPP and deliver maximum power. All the analytical, simulation, and experimental results of this study are included.