Advancement of voltage equalizer topologies for serially connected solar modules as partial shading mitigation technique: A comprehensive review

Abstract

Photovoltaic (PV) modules are serially connected in a PV string to provide a high-voltage input for grid-connected inverters. One of the stumbling blocks in maximum power extraction is the detrimental effects of partial shading condition (PSC) on series-connected PV modules/submodules. There are different types of approaches proposed in the literature to mitigate or minimize the effect of PSCs. However, in this paper, the study focused on the review of voltage equalizer (VE) topologies, a segment of circuit-based shading mitigation approaches. VE topologies increased the maximum power extraction capability during PSCs in comparison with the activation of bypass diodes by equalizing the voltages across all modules connected in series and avoids the multiple peaks generation on P–V and I–V curve. Twenty-three VE topologies were reviewed and classified into seven categories in a manner that each subsequent topology improved the prior. Each topology has been elaborated from a design perspective. Further, the topologies were quantitatively and qualitatively analyzed. Additionally, the optimized topology from each category was evaluated for improved efficiency and loss percentage using a PowerSIM software tool. For a fair comparison between each type, the same set of PSCs was considered. An experimental performance comparison between one of the efficient VE topology and conventional solar PV optimization controller proves the power efficiency improved by 60.12% for the same PSC. The conclusion was drawn based on the literature review and evaluation findings. This study provides a brief idea to researchers and practitioners about the ongoing topologies of VEs. This work also suggests future recommendations on which further research can be focused.