A novel PV sub-module-level power-balancing topology for maximum power point tracking under partial shading and mismatch conditions

Abstract

Partial shading and mismatch conditions among the series-connected modules/sub-modules suffer from a nonconvex power curve with multiple local maxima and decreased peak power for the whole string. Energy transfer between the sub-modules brings them to the same operating voltage, and this collective operation produces a convex power curve, which results in increased peak power for the string. The proposed topology benefits from the switched-capacitor (SC) converter concept and is an applica-tion for sub-module-level power balancing with some novelties, including stopping the switching in absence of shading, string-level extension, and a reduced number of power electronics components as compared to those in the literature. Reduction in the number of power electronics components is realized by the fact that two sub-modules share one SC converter. This leads to reduced power electronics losses as well as less cost and volume of the converter circuit. Insertion loss analysis of the topology is presented. The proposed topology is simulated in the PSpice environment, and a prototype is built for experimental verification. Both simulation and experimental results confirm the loss analysis. This proves that with the proposed topology it is possible to extract almost all the power available on the partially shaded string and transfer it to the load side.

Keywords

Sub-module-level maximum power point tracking (MPPT) / Differential power processing (DPP) / Distributed power converters / Switched-capacitor (SC) converters

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2016 Zhejiang University and Springer-Verlag Berlin Heidelberg