An approach to reduce the effect of partial shading on photovoltaic modules (2015)
Partial shading (PS) losses occur when some photovoltaic (PV) cells in a PV array, panel, or module are shaded from the illuminating light source. Such a phenomenon causes a substantial reduction in power generation, and it is seen to be an inevitable problem in maximizing the efficiency of the entire PV system, especially in the case of small-scale urban implementations, where the location choices are often suboptimal and shading obstacles are commonly encountered. Therefore, this thesis proposes a robust technique to reconfigure a PV module’s connection pattern in order to passively reduce the effect of PS by dispersing the shade to other parts of the module without either intensely modifying the circuitry or requiring the introduction of additional electronic devices. An ideal single-diode model of the PV cell is used to simulate and compare the performance of PV modules using different connecting methodologies, including the proposed strategy under extensive PS conditions. The proposed configuration is able to obtain improved maximum power points (MPP(s)), while displaying fewer significant disadvantages that the other shade dispersion methods have exhibited. It also shows fewer scalability limitations after ensuring the PV module is reasonably sufficient in size, as there is no requirement on the scale and the parity combination from its numbers of rows and columns. Moreover, under the placement rules of the proposed strategy, only alternating, and therefore no more than half of the columns in the configuration, are required to be changed, thus making the process modularizable, and reducing the total implementation costs. Furthermore, the resulting PV characteristic curves are shown to have more distinct MPP after utilizing the shade dispersion strategy, which become more convenient for following MPP tracking controls if desired. Finally, a PV module prototype, consisting of 6 x 6 PV cells, is implemented, and the experimental results validate the effectiveness of the proposed shade dispersion approach. The achieved MPP improvements are found to be better than the other tested shade dispersion method if the shade comes with an angle, and significantly better than the typical series-parallel or the total-cross-tied configuration when the shade is substantial in size.