Differential Power Processing Applied to a Photovoltaic String with Different Modules

The differential power processing (DPP) concept has been widely used to mitigate the negative effect of temporary photovoltaic (PV) mismatch that may be caused by shading, for instance. Permanent mismatch occurs in a PV system when the cells or modules have different electrical and/or constructive characteristics, which in turn lead to the reduction of the extracted power. This subject is an important emerging topic that has been narrowly addressed by researchers so far. In this context, this paper presents a study on the application of DPP in a PV string with permanent mismatch. A four-module string connected to PV-to-PV architecture employing the bidirectional buck-boost converter is assessed in detail. The results show that the use of a DPP converter in a string composed of modules with different specifications can increase the energy harvesting significantly.