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UBC Theses and Dissertations

Optimal shade distribution technique to mitigate partial shading effects in photovoltaic systems Aliaslkhiabani, Mahdieh


Partial Shading (PS) critically reduces the maximum power extractable from a photovoltaic (PV) array, decreasing its efficiency, and creating multiple local peaks (LP) in the characteristic P-V curve of the array. Currently, the electrical connection that minimizes the power loss is the Total Cross Tied (TCT) connection, where each panel in a string is connected in parallel to the all the other panels in the same row, creating an electrical matrix connection. Although the TCT connection reduces part of the problem, it is still sensitive to several shaded panels in the same row constraining the current. In this thesis, a new technique to reduce the consequences of mismatch conditions by optimally distributing the shade over the entire array while maintaining the TCT connection is presented. The proposed method is dubbed “Shade Dispenser” (SD), as it takes a physical shade covering adjacent cells and electrically dispenses it minimizing the occurrence of same-row shades. The physical separation of electrically connected PV panels comes at a cost: it increases the wiring cost and power losses of the array. This trade-off is explored in the proposed paper, outlining the solution for each array size. As a result, this technique represents a considerable reduction in the effects of PS while minimizing wiring losses and costs. The performance of the system is investigated under different shading patterns and compared with the most efficient existing interconnection schemes. Simulation results confirm that not only is the efficiency of the proposed strategy higher, but the payback time for overhead wiring cost is lower. Moreover, this method diminishes the number of Local Peaks (LP) in the P-V curve of the array.

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