Experimenting with a Battery-Based Mitigation Technique for Coping with Predictable Partial Shading

Abstract

In this paper, the authors propose to use batteries to improve the performance of grid-connected photovoltaic plants when their photovoltaic fields are subject to partial shading phenomena. Particular attention is devoted to predictable and repetitive partial shadings, such as those that often appear in urban residential environments. Firstly, battery packs with proper nominal voltage and capacity are connected in parallel to partially shaded photovoltaic submodules. Then, the shaded photovoltaic submodules are properly disconnected and connected to the respective photovoltaic string by using a “battery control unit”, which is operated by taking into account characteristics of the specific partial shading phenomenon to cope with. To demonstrate the effectiveness of the proposed technique, an experimental study is performed to compare the performances of two identical prototypal grid-connected photovoltaic generators subject to identical artificial and repetitive partial shadings. Only one of the photovoltaic generators is equipped with batteries together with their respective battery control unit, while the second one is simply equipped with conventional bypass diodes. The main advantages of the proposed technique are a greatly improved whole power generation together with the elimination of hotspot phenomena.

A Building-Integrated Bifacial and Transparent PV Generator Operated by an “Under-Glass” Single Axis Solar Tracker

“…To obtain this reasonable goal, it is necessary to avoid any reciprocal shadowing phenomenon that can occur during the daily rotations of the PV strings, which are necessarily installed side by side [30]. Furthermore, it is well known that avoiding reciprocal shadowing phenomena among the PV strings helps to avoid any adverse hotspot phenomenon and maintain their lifespan [31]. Nevertheless, the only way to avoid (or limit at the minimum) the aforementioned shadowing phenomena is to space the rotating PV strings properly; that is to say, an empty space must be introduced between each pair of PV strings installed side by side.…”

“…In principle, this phenomenon could cause adverse and repetitive hotspots on the shaded PV modules, which can significantly affect their lifetime. Nevertheless, without any prejudice to the opportunity of a further specific study of the phenomenon, as explained in [31], in this specific context, there are at least two good reasons to believe that this phenomenon may not be harmful. First, the low power and the low number of series-connected PV cells of the involved PV modules should guarantee very low currents, very low reverse voltages, and, therefore, very low power dissipated on the shaded PV cells.…”

“…Second, the shadowing always uniformly affects all the series-connected PV cells of all the single-row PV modules, and this means that, during an eventual hotspot, the whole dissipated power is equally distributed among all the PV cells shaded at the same time. Furthermore, since the shadowing is repetitive, predictable and known, in [31], it was shown that it can be simple to effectively cope with this phenomenon by taking advantage of the battery technology.…”

Robust Voltage Control of a Buck DC-DC Converter: A Sliding Mode Approach

“…Different DC-DC converters are used as buck converters, boost converters, buck-boost converters, etc. [31][32][33][34]. The boost and buck converters are the most commonly used.…”