A Novel Method for Least Differential Power Processing in PV Systems

Strings of series connected Photovoltaic (PV) elements suffer from severe power reduction when mismatch between PV elements occurs. Differential power processing (DPP) is used in PV systems to minimize energy conversion losses while optimizing the PV power during mismatch. One way to implement DPP is using the PV-bus DPP architecture where each DPP converter is connected between a PV element and the collective bus. The total processed power in PV-bus system depends on the substring current which is the output current of PV elements. Analytically, there is a unique operating point for this current to minimize the losses and achieve least processed power (LPP) through all DPP converters. This work represents a new methodology to control the substring current for achieving LPP in DPP system using minimum energy conversion stages. Different mismatch levels are analyzed to show that the proposed system can reach LPP resulting in a huge reduction in the processed power.