Differential Power-processing with Built-in Energy Storage for Multi-String Grid Interactive PV System

This paper introduces a novel configuration of a highly efficient self-sustained grid interactive photo voltaic (PV) system based on multi-string architecture. The goal is to achieve improved efficiency while performing Maximum Power Point Tracking (MPPT) operation during both uniform and nonuniform shading conditions. Differential Power-processing Converter (DPC) concept is adopted here for the dc-dc stage, targeting an improved Power Transfer Efficiency (PTE) for the system. The energy storage is connected at a common virtual bus instead of dc-link of the inverter, which eliminates the need of extra dc-dc converter for energy storage integration. A novel control algorithm is proposed for an effective power and energy management between generation, load, storage and grid all together, minimizing the grid interaction as much as possible to make the system self-sustainable and cost effective. Last but not the least, this paper also proposes a novel seamless Mode Transition Algorithm (MTA), which will ensure that the DPCs are completely bypassed during uniform insolation condition to improve all-day efficiency of the system. The proposed algorithms and associated control methods are implemented in MATLAB/Simulink environment for a given set of generation and load profile to verify the concept.