Increasing Energy Capture from Partially Shaded PV String Using Differential Power Processing

摘要： In PV strings based on series-connected PV modules, mismatches among the modules due to partial shading, will cause in power loss either due to series connection constraint or due to bypass diodes. This paper proposes a new distributed MPPT (DMPPT) scheme using multi-winding forward-based converter, acts as a current balancing differential power processing (DPP) converter. The converter is configured in the way that each converter port is connected in parallel with individual PV module to enable module-level maximum power extraction. The proposed architecture operates in two modes: local MPPT mode and current balancing mode. The new MPPs at module-level are tracked in local MPPT mode and then dispatched to start current balancing mode of operation. In the current balancing mode, this paper proposes a simple control approach to maximize output power from partially shaded PV string by maintaining an effective MPPT at module-levels and directly transferring the compensation currents toward the shaded modules from modules under normal conditions without any intermediary. The proposed DMPPT scheme is validated by simulation and experimental results. The results show that using the proposed scheme, the system efficiency is significantly improved compared to other existing topologies.