Maximum power point tracking method for improved string photovoltaic system under partially shaded conditions

This paper proposes an improved string photovoltaic (PV) system to increase system power quality. The proposed structure can change operation mode according to the degree of PV strings shaded. When all strings are uniform, the system works in central mode. When one or more strings are non-uniform with others, the non-uniform strings separate from central mode, and operate in string mode. In this condition, multiple peaks can be exhibited on the power-voltage characteristic curve. To solve this problem, a global searching maximum power point tracking (MPPT) method is presented and implemented. Simulation and experimental results indicate the feasibility of the proposed work.